Worse, sitting up in bed, she recognised nothing. Walls that should have been covered with teenaged decoration were dismal and grey. The curtains were different. Her Marilyn Monroe duvet cover was nowhere to be seen and her sister's bunk bed was missing.

She stumbled down the foreign hallway and pushed open a bathroom door. When she saw her reflection in the mirror, her jaw dropped in horror.

"I grabbed my face and screamed, 'No! Oh my god, oh my god, oh my god ... I'm OLD!'"

Ms Jacobs was 32, but she had lost 17 years of her life to a rare amnesia. As far as she was concerned, she was 15.

I Woke Up In The Future is her account of forgetting almost two decades and getting a second chance to turn around a life wasted on addiction and regret.

Over a Skype call from her hometown of Manchester, Ms Jacobs, 39, says it doesn't matter how often she tells her story, she remains as fascinated by her "remarkable life" as might any stranger.

"I think I need a thesaurus for more words other than 'shocked' or 'terrified', but that's how it was. Imagine waking up knowing you're 15 but finding out you're 32. I was gripping the wall in fear."

Ms Jacobs was through the rabbit hole. But amid the surreal confusion, one phone number kept repeating in her mind. She dialled Katie, a friend who made some sense of the garbled sobs coming down the phone and advised Ms Jacobs to have a coffee and cigarette to calm herself down. Both suggestions were disgusting to Ms Jacobs, who at 15 had never liked the taste of either.

She could remember certain phone numbers, how to drive a car and how to use a cash point, but had no recollection of giving birth to her son, Leo, at 21. She was even using the lingo of her youth, she says, calling people "smegheads" as per '90s TV show Red Dwarf.

As her sister cautiously explained "adult" Naomi's life, "teen" Naomi could not understand how, despite all the dreams she'd had for her future, she had become a single mother in a two-bedroom council flat.

There was so much to catch up on: Ms Jacobs spent hours online watching piano-playing cats, kids drugged up after dentist visits, crop circles and conspiracy theories. She sobbed over the 9/11 attacks and the "War on Terror".

Her new world was filled with the weird clarity of high-definition television screens and mobile phones that were no longer the size of backpacks. And the explosion of social media meant everybody had an opinion. She felt like the whole population was desperate to be heard.

Staunchly believing a few nights' sleep would bring her memory back, she held off seeing a doctor for days, but it took months before she would find a psychiatrist who could diagnosed her correctly. It was transient global amnesia combined with a dissociative fugue state.

"He told me it was the remarkable product of a remarkable life and I just sobbed with the relief of finding out that what I had, had a name."

Luckily, Ms Jacobs had religiously kept diaries throughout her life; her journals dated back years and reading them helped jog her memory.

"It was a bit like reading The Secret Diary of Adrian Mole mixed with Bridget Jones," she recalls. "It was an emotional roller-coaster; I felt joy for the person who'd written it and sadness for her too.

"Slowly, things came back to me. It was like looking at the ghost of my adult self. I'd hear a song and get a flash of a basement club, so I'd ask my sister if we'd done something like that and she'd say yes. Then I'd start to feel emotions attached to the memory, but not the whole thing.

"I had a sense my body had given birth - when I first saw Leo it was a really powerful rush of love; a real dry-mouth moment. He had my cheekbones and a little Afro. He was a mini-me."

Reading the diaries made Ms Jacobs realise she had been under immense stress leading up to the amnesia. In the past she had been diagnosed as bipolar and had psychotic episodes; each time her life appeared to be straightening out, adult Naomi returned to marijuana and cocaine. She'd been in abusive relationships and had friends who cared little for her welfare.

The diaries were her "saving grace". It was in those pages she kept secrets about adults who had sexually and physically abused her.

Writing I Woke Up In The Future was a cathartic experience and allowed her to let go of those demons, she says.

"I was angry, I was scared and I needed answers. I knew it was time to get real. I had to expose everything in my life and really face up to it.

"In the past, I'd turned to weed. I'd reach a point where I couldn't cope and I'd roll a joint or take cocaine, but that wasn't attacking the issues. It was just burying everything."

There was a certain amount of worrying when it came to writing about her friends and relations.

"In the first draft I [wrote] how I'd got a shock seeing my sister for the first time. I called her a matronly apple shape, but the editor asked me [to be more honest about] how I really felt. Well, it was more like, 'Oh my god, she's fat,' so I had to learn to be honest.

"Mum and Dad are both happy I've done the book. I tried to be sensitive - Mum and I had a difficult relationship growing up, but I didn't want to turn her into a villain. That wasn't the point. She had her own issues and there had to be some element of forgiveness. It was a second chance at my own life and I'm not judging anyone else."

The old her, she says, just wanted to see her son through school so she could curl up and die. "When you feel like you're always getting pushed back by life you essentially give up on yourself. Amnesia was my mind's way of saying, 'You cannot carry on like this any more.' "

Ms Jacobs got her memory back; mostly it came back within eight weeks, but getting to the very bottom of it took years. "Now I'm in a very fortunate position," she says. "I'm still in my two-bedroom house with my cat. My son is now 17, doing an apprenticeship in digital marketing. I'll be 40 this year and I just have this lovely feeling of self-acceptance.

"I'm not perfect, I still have my bad days, but I have a firmer handle on my mental health. I can run five kilometres, I sleep better, I no longer take drugs. Even if it's a bad day, I make sure I laugh and I never have to go past Leo for that. He's a walking comedy, that boy.

"I'm not afraid any more, and when people ask if I could give back the whole thing and be living like the amnesia never happened, no way. I wouldn't change it for the world."

I Woke up in the Future is published by Macmillan.

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