'So… wait," I asked my friend Hayley, over some overpriced wine in my local one evening, "you don't use any contraception, at all?" "None," she said matter-of-factly. "I've had unprotected sex so many times with no results that I think I might be infertile." I doubt that she needed my judgment face at that particular moment, but she got it. She's no teenager, and I have to admit I'd thought she would know better.

Unprotected sex. At one point or another, we've all had it (haven't we? Haven't we?). I've stopped asking my friends if they've used a condom when we do our regular one-night-stand postmortems, not because it makes me look like a neurotic teenager, but because I know that they haven't. And I have no idea how we, well educated in the dangers of unprotected sex and way past our teens, have got to this stage. I am shocked, when canvassing my friends, that in taking the contraceptive pill I am in the minority. Some friends are using other methods, but others aren't using anything. They are just styling it out. Bareback.

I'll admit, I've been lackadaisical with contraception myself (Dad, if that isn't enough to make you stop reading now, then I don't know what is) and have taken the morning-after pill six or seven times (perhaps that?) so I'm in no position to be casting stones, but my several trips to the genitourinary medicine (GUM) clinic for various tests (including one for HIV) were scary enough to convince me that I had been conducting myself like a fool. Add an abnormal smear test result into the mix (pre-cancerous cells on the cervix are usually caused by human papillomavirus, HPV; up to eight out of 10 people will be infected with it at some point. As a character in Girls says, "all adventurous girls" have it) and I became pretty convinced of the importance of strapping it up.

In the UK, sexually transmitted infections are on the rise among all age groups, as is the abortion rate. According to Public Health England figures, STI diagnoses rose 5% in 2012, with those under 25 experiencing the highest rates (they account for 64% of chlamydia cases). Public Health England acknowledges that this is in part to due to improved data collection, but also warns that "the continuing high STI rates in England suggest too many people are still putting themselves at risk through unsafe sex, especially young adults and men who have sex with men". That young people engage in risk-taking behaviour will be a surprise to no one, of course, but what is interesting is that we're seeing such behaviours in those who are mature and responsible in other parts of their lives. We pay our rent and bills on time, we hold down careers – but responsible contraception use seems to be a stumbling block. We don't have the excuse of a lack of education to fall back on. While there are problems with the way sex education is taught, vagueness about contraception and the mechanics of sex does not appear to be one of them (many people I spoke to recall the infamous cartoon Johnny Condom song, a source of much classroom hilarity).

Some even claim that twentysomethings are the poster demographic for unprotected sex. The increase in risky sex among my age group (I am 26) led to American journalist Ann Friedman describing us as the "pull-out generation". As monikers go, I have to admit it's not my favourite, but it does resonate. Most of my friends have admitted to having used this fallible and messy technique to avoid pregnancy, while some rely on it as their only method of contraception. "These women describe a deliberate transition from the pill to the pull-out," wrote Friedman. "They buy organic kale and all-natural cleaning products, and so can't quite get down with taking synthetic hormones every day. They see orgasms as a right, not a privilege."

Pulling out has, for me, never really had much to do with kale. In my group of friends, it seemed to be something that occurred accidentally or due to poor organisation. Penny Barber, area director for sexual health service Brook in the Midlands, agrees: "Typically we hear that young people have unprotected sex because they ran out of condoms or pills, or they had too much to drink."

According to the Family Planning Association, there is scant research on modern use of coitus interruptus (which they describe as "the oldest form of birth control practised today") in Britain, but an American study conducted by Duke University last year found that 31% of young women in America aged between 15 and 24 had relied on the withdrawal method at least once.

I was interested to find out whether or not we are seeing a more conscious shift away from hormonal contraceptive methods in favour of the pull-out method. The most recent figures available on contraceptive use are from the Office for National Statistics from 2008-2009. They revealed that the majority of women under 50 were using contraception (75%), with condoms (25%) and the contraceptive pill (25%) the most popular methods. Of those women who weren't using contraception, just over half were not engaged in a sexual relationship with a member of the opposite sex. But that was more than five years ago. Could it be true that women are being turned off the pill and condoms, too? Among the many twentysomethings I spoke to from all over the UK, it would appear so.

Alex, 24, a charity worker, says that unprotected sex is something that she and her partner go through in phases, "depending on how sensible either of us is feeling at the time", and that a dislike of condoms is a factor. She has relied on the withdrawal method in the past and has had chlamydia, gonorrhea and one pregnancy scare. She has made a conscious decision not to take the pill: "I have never taken hormonal contraception and I can't see me ever wanting to take it; there is something about the idea of adding hormones to my body that I just hate. Perhaps it's the fact that they can change your mood. During my MA year, one friend slept her way through an entire city using nothing but the pull-out method and remained pregnancy- and disease-free – while at the same time I got chlamydia from sleeping with one man for eight months." Despite having contracted an STD, Alex is philosophical about her methods, as were many of the women I spoke to. "I see unprotected sex as a choice made by adults, and as a fairly intelligent and informed adult I take responsibility for any consequences," she says.

Elise, 32, uses withdrawal with her long-term partner and is similarly laid-back. She is perhaps what you'd call "pregnancy ambivalent": "I don't have the terrible anxiety about accidental pregnancy that I had when I was 20," she says. "We both hate condoms and I got tired of taking the pill. I couldn't settle on one and had to keep going back to the doctor with bleeding. I ended up saying I'd take a break and never went back."

When Elise was younger, it was different. Although she says she was worried about getting pregnant, she did have unprotected sex at least five times. It was, she says, a period "characterised by carelessness and drunken decisions at a time where I didn't feel anything bad would happen to me. I think some of the men would rather I had insisted we use a condom but didn't speak up themselves.

"I was very lucky not to get pregnant, or to get an STD worse than the almost inevitable chlamydia I ended up with. When the GUM nurse called me to tell me I had chlamydia I was overcome with relief. I think she thought my reaction was inappropriate." Inappropriate, perhaps, but not unusual – many of the women I interviewed admitted they were much more concerned about unwanted pregnancy than they were about STIs, and chlamydia, which is treated with antibiotics, no longer seems to strike the fear of God into young women.

But it's not just youth that can make you feel invulnerable, as Danni, 32, a communications manager, explains: "Very few single women I know would use condoms with any regularity. I've had unprotected sex with about 15 men, in relationships and casually, and I can say I've used a condom about three times. I'm not that confident about using condoms – putting them on. Guys seem to hate them, and sometimes, I'm too drunk or turned on to care."

The idea of condoms not being conducive to spontaneity – especially drunken spontaneity – is cited as a reason for rejecting them again and again, as is pressure from men. Gina, 29, an IT helpdesk supervisor, has had unprotected sex while drunk but says she wouldn't do it now, having once contracted chlamydia. I can understand young people in their teens feeling too embarrassed or intimidated to broach the subject of condoms, but I expected women who are a bit older to feel more confident and assertive when it came to contraception. Then I thought about all those morning-after pills, and remembered that I hadn't been, either.

At times, the young women I spoke to seemed to resent feeling that they had to take responsibility for contraception. "I've never felt personally pressured by a guy I've slept with not to use a condom – most have been absolutely fine with it," says Beatrice, 20, a student. "However, none of them took the initiative to suggest using one." She blames a lack of confidence for the fact that she has had unsafe sex more times than she can count, saying that she takes emergency contraception and has regular STI tests "due to my inability to question guys I sleep with on their own testing history".

A failure to communicate was a common factor, which makes me question whether British sex education – which focuses very much on the mechanics – might have a lot to answer for after all. I also wonder if porn – not renowned for its on-screen condom use – might play a part. Sex educators seem hellbent on convincing young people that condoms can be sexy and often provide them with tips and tricks to make the experience more erotic. Perhaps they'd be better off encouraging better conversations. It wasn't that anyone I spoke to didn't know how to use condoms, or that they were one of the few methods that protected against STIs, it was that they didn't feel they had the language to talk about them. Gina said she felt unable to bring up the topic: "I'm unable to ask, or stop someone when they have gone that far." Harriet, a 23-year-old student, agrees. "In the past I have definitely felt ashamed to ask someone to put a condom on, kind of like you're being a bit of a bore. Never in my whole time of sleeping with guys has one of them done it or offered." She has had unprotected sex with one-night stands roughly 15 times – "I always just thought I'd get the morning-after pill" – and she eventually got pregnant and had an abortion. Four of her friends have also had abortions following unprotected sex.

Male distaste for condoms isn't the only reason unprotected sex takes place. There's also the fact that the side effects of the pill are too much for some young women to bear. Like many of the young women I spoke to, Harriet's reasons for using withdrawal or having unprotected sex were partly as a result of male pressure not to use condoms, but also because of a genuine discomfort with the possible side effects of hormonal contraception. "The [contraceptive] pill sent me crazy. There was a definite change in my moods and when I wasn't sleeping, I was screaming or crying… it put me off for good," she says. "I fell head over heels for someone. The thought of putting anything hormonal back in my body scared me but he refused to wear condoms. Every time I'd get a period it would just be like a green light saying, 'You're not pregnant! Carry on!' Obviously the day came where I was pregnant. I had the op" – meaning an abortion – "and at the same time had the implant shoved into my arm. Six months of what can only be described as hell followed. I was constantly bleeding and I went into a deep dark depression."

Scare stories about hormonal contraception hit the newspapers every few months. In January, doctors were advised by the Medicines and Healthcare Products Regulatory Agency to warn patients taking "third generation pills" including Yasmin, Femodene and Marvelon, that they are twice as likely as older medication to cause life-threatening blood clots. (The risk applies to women who are already more likely to develop clots.)

It's no wonder that women are hyperconscious of potential side effects. Holly Grigg-Spall, author of Sweetening The Pill: Or How We Got Hooked On Hormonal Birth Control, says that side effects such as depression and loss of libido steer many women away. "I felt oppressed by the pill," she tells me. It was when she started a blog on the topic that she realised other women felt the same way. "Many women don't want to be taking these drugs any more," she says. She endorses a natural family planning method that involves combining a period tracker app with other indications of fertility, such as cervical mucus and body temperature, to work out when it is safe to have sex.

"There are two camps," she says. "[There are] women who haven't used condoms for a long time or don't want to use them, and rather than using condoms as a stopgap they just decide they'll use the withdrawal method." Then, she says, you have those who use the (little-understood) fertility awareness methods, noting their cycles to work out when they can have sex. "We also have this movement of women who are really interested in learning about their cycles so that they're very much in control of their bodies." It's true that the pill can play havoc with libido, but with all of society's technological advances, isn't returning to the "old way" of doing things a little bit backwards?

"It's a real shame that natural family planning is getting confused with the withdrawal method," says Natika Halil, of the Family Planning Association. "It's a form of contraception and it is 94% accurate when used properly." Grigg-Spall agrees that the confusion has not been helpful, and the boom in period tracker apps has added to the confusion. "They can try to say when you're going to get your period but these apps shouldn't be telling you when you're fertile, because they don't know," she says, emphasising that there are apps available that capture more data and so are much more reliable. Fertility awareness is a method of contraception that has, according to the figures available, very little uptake in Britain – less than 1% of sexually active people – and Brook doesn't recommend it for those under 25 "as it doesn't tend to fit in with their lifestyles". (She's not wrong: I struggle to envisage myself taking the time out of freshers' week to check my cervical mucus.)

From my conversations with women in their teens, 20s and 30s, there is certainly a sense of dissatisfaction with the contraceptive options available. For every woman who says that she felt pressured by men into not using condoms, there's another who says that she dislikes the sensation. Many, like Frieda, 27, are also wary of the pill. "I just didn't feel right on it. I felt less sexy and a little bit depressed," she says. "I came off it and was horrified not to have a period for six months. I didn't like that I had been altering my natural state for so long." Frieda also dislikes the implication that her methods are irresponsible. "I have a very regular period and know when I ovulate, so I go by that."

Dr Georgina Noble, a specialist in integrated sexual health, is quick to point out that, unlike in America, the NHS makes it easy for female patients to try different kinds of contraception; in the US, insurance companies will cover only certain types, so there's less freedom to experiment. Working in a GUM clinic, she's much more likely to see withdrawal used by teenage girls who haven't yet found out how to get access to contraception. "They don't consider condoms, they think, 'It's OK because he pulled out.' Eventually they pluck up the courage and tend to come to the clinic in a group with their friends."

She's quick to highlight the risks of using the withdrawal method. I hadn't heard pre-ejaculate referred to since I was a reader of teenage magazines, which were obsessed with it, but Noble cites a study indicating that sperm is present in 41% of samples. Noble also mentions a patient who had never had penetrative sex and yet became pregnant through contact with pre-ejaculate.

Luke, 25, told me a similar story. "Unwanted pregnancy has happened to me twice. The first time, the first relationship I was in, I got a girl pregnant from using the pull-out method," he says. "It was through the magic of pre-come. It was quite stressful as a 17-year-old." The second time he made a girl pregnant was due to a defective coil. "It's made me massively more careful now." Noble says that most women are happy on Microgynon 30, the default contraceptive that the NHS offers, and, though she admits there can be some side effects, these might be bearable considering the alternative. "Pregnancy is also life-altering," she says. "I want my patients to get the most effective contraception that is acceptable to them. I take hormonal contraception and am happy to recommend all hormonal and long-acting reversible contraceptions to friends and family."

Many of the women I interviewed expressed regret at the fact that they had used the withdrawal method or had unprotected sex when they were younger. Elise, for instance, says, "There's no excuse for being so stupid and I don't know why I did it." Jane, a 32-year-old civil servant, caught chlamydia when she was 19. "I have never felt so dirty," she says. "I wish I'd used a condom. True, they make sex less spontaneous, but I'd swap that for an internal examination and accompanying swabs, quite frankly."

There's a palpable sense of embarrassment from those who feel that the unprotected sex they had was a result of carelessness. Several of my friends avoid the pill because of concerns about weight gain, despite the fact that studies reveal it to be minimal. Others, like Harriet, find the mood swings unbearable. Having had an abortion and been fitted with the implant, she finally had it removed and went back to relying on the pull-out method. Earlier this year the National Institute for Health and Care Excellence (Nice) recommended that young women should be allowed to keep a supply of the morning-after pill at home in case they need it. At the moment you can purchase only one pill at a time, but the British Pregnancy Advisory Service has argued that allowing women to buy packets of pills will reduce the number of unwanted pregnancies. In the same report, Nice also recommended that health professionals not be too quick to prescribe the contraceptive pill, and to make other long-acting methods available to all young women.

So has the pill liberated us? On the one hand, I am of course relieved that I can have regular sex and not get pregnant. But on the other, after speaking to so many women who would rather use withdrawal because of the side effects, I agree with Grigg-Spall that we have become blindly accepting of its use. "It's very difficult to criticise publicly," she says. "Sexual liberation has trumped other kinds of liberation. We've basically linked hormonal birth control with sexual liberation, which is interesting because many women experience a negative impact on their sexual libido. And that is apparently fine."

Grigg-Spall points out that there has been a long history in the women's movement of ambivalence towards the pill, but that objections have been sidelined. "The pharma industry has a real grip. We've been led to believe that the choices women have are hormonal birth control or pregnancy and nothing in between. "Women having unprotected sex, relying on withdrawal – they should see that as a warning sign that we're not doing enough.

Harri Wright, 25, exams officer, in a long-term relationship

I've had unprotected sex probably hundreds of times. I've been in a relationship with my boyfriend for eight years, and more often than not we don't use any form of contraception. I had been on and off many different kinds of pill – because of moving around during my university years I wasn't able to settle on one. The hormones always made me feel a bit weird and later on I started experiencing nausea. In the end my partner and I were happy for me to stop taking the pill. We've never consistently used condoms as neither of us like the feel of them.

Pulling out is our main method of contraception. I keep an eye on my cycle and we avoid peak times or use a condom. We would prefer to plan a pregnancy, but a surprise wouldn't be the end of the world. We wouldn't have made the decision for me to come off the pill if we didn't feel we could handle the repercussions.

Jess Tyrer, 23, travel advisor

As a teenager I was vigilant about my sexual health, but after a couple of years, my friends and I became more lax with contraception. We were being irresponsible and testing our limits.

I've had unprotected sex quite a few times, and I used the pull-out method with my former partner. Looking back, I don't think we even discussed it. Naive as it sounds now, I didn't really have any worries about STDs or pregnancy. I knew that neither of us had any STDs, and with other people, if we did have unprotected sex I always went to the GUM clinic.

Unprotected sex happens for several reasons. It may be that you don't want to stop to put a condom on, sometimes you may be embarrassed to ask your partner, or they may think that you have an IUD or are on the pill. Obviously if you have been drinking, that increases the risk.

I think I'm more mature now. I sort of want to go back and shake the younger me and make her see sense.

Emma Alfonso, 26, business owner, single

I've had unprotected sex with five different men, three of whom I was in a relationship with. The other two were casual.

It starts when you are a teenager and your loving boyfriend suggests you don't use a condom, because he'll lose sensitivity. You, being the cool, chilled out kind of girl you're desperately trying to be, go with it. Once you've done it once and survived, you lose the fear.

Condoms are disgusting and sometimes funny, and no one wants to feel those emotions when having sex. No matter how you colour, flavour or add little ribs and dots "for her pleasure", condoms are a mood killer.

The pill is a pain to keep track of and has caused me and my friends horrible side effects from headaches and acne to weight gain and mood swings. Similarly the contraceptive injection turned me into a "psycho bitch from hell", according to my boyfriend. Then there was the coil. I was one of the 0.1% that managed to get up the duff anyway with it in. Not that I am complaining, my daughter is a delight.

Many people would judge me for having unprotected sex but it is a risk I take in the same way I don't always use sunscreen, and I binge drink. Having unprotected sex is one thing, but not getting checked and having unprotected sex when you're not sure whether you are "clean" or not is quite another.

• Some names have been changed.