For artist and writer Charlotte Amelia Poe, 30, every day feels like a walk across a frozen pond. “It’s how it’s always been,” she explains. “You’re trying to navigate it and stay safe, but you’re aware that at any moment the ice is likely to crack, and at that point you will sink into the water.”

The worst of it is that, when she feels that way, she has no idea how she can avoid going under. “You think you’re doing fine and you’re treading carefully enough not to crack the ice. But suddenly you’ve gone under. You’ve got it completely wrong – and you’ve no idea why.”

Poe is describing how it feels to be autistic. She wants the rest of us to understand, she says, because it really matters, perhaps more than it’s ever mattered (of which more later). Her mission to break open the mystery of how it feels to be autistic has already been impressively successful: last year she won the Spectrum art prize for her video piece How To Be Autistic and recently she wrote a book of the same name. Her hope is that, by opening up about her own journey through childhood, school and adolescence, she can change other people’s perceptions and expectations about what autism is like, from the inside.

We are talking in the sitting room of the semi-detached house overlooking a Suffolk field that Poe shares with three generations of her family. She has never left home and doesn’t expect to; her nephews and niece are playing outside in the garden, and one day their mother, her sister, will be her carer in the way that her parents are at the moment.

“It’s a scary feeling, that I’ll be inherited,” she says. “But I’d be very lonely if I had to live alone. I need people around me. I like noise and I like being surrounded by people I love.” She’s curled up on the sofa as we speak, her legs tucked underneath her, looking fragile and bird-like, but her voice is surprisingly strong, as well as impressively articulate.

Poe was just six or seven years old and at primary school when she realised she was different. Astonishingly, it wasn’t until she was 21 that she received a diagnosis of autism. The reason, she says, is simple – society looks for autism in boys, not girls, and the way it presents means that boys are more likely to be identified with it. “Autistic children are often quiet and obedient when they’re very young – and if you’re a girl, that’s not unusual. But for a boy it is. If I’d been a boy I’d have been diagnosed years sooner.”

That rankles, because at school she knew autistic boys and they had an easier time of it because they had a label – “Sometimes labels can be really helpful,” she says – and she describes how she was increasingly seen as awkward by her teachers, some of whom bullied her as much as some of her fellow pupils did.

“If I’d been diagnosed sooner,” she says, “I wouldn’t have had the level of trauma I’ve had. It makes me angry that I have to deal with extra baggage that could have been avoided.”

It was people’s attitude towards her, rather than the condition itself, that made life so unbearable. “Understanding is so important – that’s what makes a real difference,” she says. “We need trained people to support us, and there aren’t enough of them – and although there’s been more awareness of autism in the past few years, it’s not filtered through into proper training. My brother is a doctor and I think he spent one day on it in his entire time at medical school.”

There are so many misunderstandings, she says. To take just one, autistic people are not unable to empathise. “It’s the weirdest thing, but people with autism get what others are feeling to a huge degree. It overwhelms us – that’s why we often don’t know how to respond, how to deal with it.”

One focus of her difficulties, for several years, was her teeth. From the time they began to wobble she was unable to brush them. She’s not sure why she found the loss of her milk teeth so disturbing, but she speculates that it may have been because “autistic people are extremely sensitive to sensation, to change, to pain”. The net result: “I went through the entirety of first school and half of middle school with a mouth full of disgusting, stinking plaque.” Although her teeth are fine now, she tries not to show them when she’s talking or smiling.

Having terrible teeth was one of the many things that made Poe stick out as different. She also had a tendency to vomit in public when her anxiety became too much to cope with (she ended up carrying a sick bowl around with her wherever she went, just in case). She was a picky eater and was unable to eat even a packed lunch at school – and she spent more and more time on her own in her bedroom.

Academically she did well, although once homework got serious she found it increasingly difficult to tackle (“That’s called executive dysfunction – you know you should do something, but you can’t bring yourself to do it”) and that led to her being seen as difficult.

Eventually, she started playing up to her profile. “You think, if I’m going to be seen as this, then it might help to just be it.” But as things would turn out, it was embracing her sense of “otherness” that led to a way forward, and gradually, being “different” became something she celebrated, rather than hid.

She turned her attention to something she says is deeply ingrained in the autistic psyche – fandom. From Harry Potter to Captain America, she became a groupie, attending conventions and dressing up as her favourite characters. It felt like a liberation. “Fandom conventions are full of people with autism,” she says. “They’re somewhere we can be unashamedly who we are.” That’s because hyperfixation, she says, is both the best and the worst thing about being autistic. “You become very fixated on something – it’s very helpful when you’re working on a project, like writing a book for example, because you can write 20,000 words in a day. But it has very negative connotations for others – people who are over-enthusiastic about stuff are written off as “autistic” – and that devalues your opinion.”

Today Poe looks as different as she feels. Her arms and legs are covered in tattoos and, on the day I meet her, her hair is dyed blonde with hues of light pink and pale blue. Being autistic still limits her life – agoraphobia means she only manages to leave the house once or twice a month, and she has to take tranquillisers first – but stumbling on the existence of the Spectrum art prize for people with autism, and then making the winning video, changed her life.

She’d like to become a fiction writer, and is currently working on her first novel – but she’s also committed to telling it like it is about autism. And that matters because, she says, autistic people, once diagnosed and understood, have great potential – they’re often very effective individuals who can make a noise and a difference. “We don’t have the same filter as neurotypical people and that can make us powerful and strong,” she says. “Look at the environmental campaigner Greta Thunberg, for example.”

And there’s more, she says, because we live in a time when people who are “other” are increasingly dismissed, cut out of the action – and those with autism, who naturally identify as outsiders, can be effective champions for all outsiders. “We really get what it means to not fit in. And with the rise of populist politics and an insular society, at a time when the notion of ‘us versus them’ is increasingly common, people with autism have really important viewpoints and experiences to share.”

Her most important point, though, is also her simplest. “If there’s one thing I’d like people to take away from my experience, that would help others with autism, it’s this: be kind,” she says. “Kindness is underrated. You don’t need to know their story, you just need to think about being friendly and helping, rather than deciding they’re strange or worthless and moving on fast. A little bit of kindness can make the world of a difference to someone who’s struggling.”

How to be Autistic by Charlotte Amelia Poe (Myriad Editions, £8.99) is available for £7.55 from guardianbookshop.com