I'm 27 and have been with my partner for five years, living with her for four. Things moved quickly at first, with talk of marriage and children, both of which I don't think I want. She says that a time may come when her maternal instinct outweighs her desire to stay with me, but I feel I may remain equally unprepared to compromise on this issue.

She has awesome talents and qualities which I love, but is not particularly cerebral, and I'm frustrated that she rarely engages with me intellectually. We bicker, but in general we're open and loving with one another and agree on important things (barring marriage and children). I feel secure and happy, but also stuck and old.

Recently I met someone who makes me feel like a teenager. She is a teenager - she's 17. We met through a project we were involved in and, although we haven't seen each other since it ended, we've exchanged long and occasionally flirtatious emails.

In a sense, age is immaterial: she's funny, politically aware, challenging, strong, talented and beautiful. But she obviously lacks maturity and experience. I know I mustn't take advantage of her. I want her friendship, but I'm kidding myself if I say I don't want more than that. Is this an early seven-year itch? Should I master my urges and grow up? I've been an inadvertent cad before and I don't want to hurt anyone. What should I be asking myself?

Look to the future

I was with a man like you for six years during my 20s, and my former partner is now 40. He was forever saying that he didn't know what he wanted out of life and was unsure if he wanted to get married and have children.

I became pregnant, totally unexpectedly, in my late 20s. He went into overdrive, telling anyone who would listen how trapped he felt and how he was too young for the responsibility. He eventually embarked on an affair, which he no doubt saw as his exit strategy.

I look at him now and I actually feel sorry for him: all his friends are married with families and are uninterested in going to the pub or a game of five-a-side now. He is overweight, lives alone and his career is going nowhere. He has told me that he bitterly regrets walking out on me and denying himself the chance to watch his son, who is now 10, grow up as part of a loving family.

It's all very well wanting to have "no ties" when you're 27. But what about when you're 37 or 47? Studies show that married men are much happier and healthier than those who never marry or have been divorced.

Bear in mind that it won't be long before 17-year-old girls start seeing you as a dirty old man, rather than boyfriend material.

Name and address withheld

Be straight with her

You owe it to your partner to be honest with her: tell her that you don't ever intend to marry her or to have children. If she wants to get married and have kids, she needs to know that if she stays with you, she won't be able to have the future she wants. If you don't know by now if you want to marry her, and you're fantasising about having affairs with teenage girls, then you're not the one for her. She deserves the chance to find someone who is.

JC, Edinburgh

Make your own choices

You should choose neither of these women, but you should start making some choices about your life, rather than coasting along with the status quo. Meeting this 17-year-old could be seen as a catalyst for action: it has given you some insight into aspects of your current relationship that you are unhappy with. However, you can also see how the age gap between you and this teenager means that a relationship with her isn't viable.

You are clearly ambivalent about your current partner and this may not be solely due to the conflicting views you have surrounding marriage and children. Perhaps you need to stop seeing that as the stumbling block.

Your relationship sounds as if it is functioning as many do, but you feel stuck. This means that you need to think about how you want to move forward. That process may involve being on your own for a while, though.

HM, Leicestershire

Don't kid yourself

I've been with so many men who seem to always be on the lookout for something better, rather than building on and improving what they have. The attraction that you feel for this 17-year-old woman is a classic case of diverting your attention from the situation you are in.

She's not the solution to it, though. She makes you feel like a teenager because, as you say, she is a teenager! It's far more appealing to get carried away with fantasies of a new, seemingly perfect relationship, than it is to sit down and deal with the painful truth that the one you are in now is not working.

Don't kid yourself that deep-rooted differences, such as whether each of you wants to have children or not, will magically vanish. Ask yourself if you want to continueliving with a woman who wants completely different things out of life to you.

There's no such thing as an "inadvertent cad": you are a 27-year-old man and as such you need to accept responsibility for your actions and start considering other people's feelings more.

Making your partner spend more time in limbo than she has done already could be supremely painful for her. You also need to be mindful of the 17-year-old's feelings. However mature you think she is, she is also vulnerable.

Name and address withheld

What the expert thinks - Linda Blair

The key question that you need to ask yourself is whether or not you feel that the source of your restlessness lies within you, or whether it's primarily a result of your current circumstances.

You say you've been an "inadvertent cad" before, so this is evidently not the first time that you've felt this way while in a relationship. Do you think that what you're feeling could be part of a more general pattern?

Once you have established and settled into a relationship, do you then start to feel trapped and find fault with your partner? Do you become bored easily in other situations? Do you find it difficult to relax and accept what you have in your life generally?

If so, then your current dissatisfaction is probably more about your ongoing need for excitement than it is about anything in your relationship - and even less about the teenager you've met. After all, you hardly know her, really, and even at this early stage you've noticed potential problems if you were to get together, such as her immaturity. Many of the qualities you have chosen to mention about her could probably be applied just as easily to your partner. If this girl is someone you think highly of, surely you wouldn't want her first serious relationship to be one that necessitates cheating on, lying to and hurting someone else.

Comparing their qualities is unlikely to help you to find contentment. Choosing someone to have a fling with is primarily hormonally driven, and defies logic. Choosing someone for a long-term commitment, on the other hand, does involve careful thought. You want to look for someone who shares your strongest values, and whom you enjoy helping to find fulfilment. It's all too easy to choose a subset of the vast array of qualities each of us possesses, and then make a comparison between potential partners. At any rate, we usually do that simply to justify something we already want to do.

If you feel that the problem is your own habitual restlessness, then this feeling will recur in every relationship you establish. If that's the case, wouldn't it be better in the long term to look for other challenges outside of your relationships?

You may consider applying for a new job, or going for promotion in your current employment. You could take up a new sport. You could join a political or environmental-action group - this would have the added advantage of satisfying your desire for intellectual sparring. Or perhaps you could plan a holiday with your partner.

On the other hand, the problem may be that you're no longer convinced you and your partner have enough in common to stay together and be happy. If you are concerned about your differing interests, you could suggest that you give one another more independence when organising your personal leisure time.

If you are worried about your different attitudes towards having children, a compromise is more difficult to find - but it's still not impossible. Talk to your partner to see if you can resolve these issues. If you can't reach an agreement, you may have to decide to separate. Only after you've parted, and you have re-established your own life, would it be a good time to look for a new partner.

Next week

I want my kids to meet my new partner

My wife and I separated last year. We have two boys, aged nine and 11, who live with me. I started dating someone six months ago and my wife is also seeing someone now.

I would like to introduce my new partner to the kids and work towards us all spending a whole day out together some time later in the summer, but my wife thinks that this is too soon for the children to handle. We both agree that the introduction of new partners into their lives needs to be done slowly and carefully. The children know I have a new partner and they say they are happy to meet her. My wife has also spoken to them about this and got the same response.

Neither my wife nor I feel we are being unreasonable, but we cannot agree. I'd like to hear readers' experiences or opinions on the timescales of introducing new partners and what worked for them. What is the acceptable amount of time to wait before introducing a new partner? When could a partner spend an evening with the kids? When could they spend a family day out with them? And when could they sleep over?

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