The model and actor Cara Delevingne has said the depression she suffered as a teenager left her feeling alienated and suicidal.

Delevingne, one of the most recognisable faces in the world – she has fronted campaigns for Chanel and Burberry – spoke about how she was often mistaken for a boy when she was younger.

“If I wore the clothes I liked, with my short hair, everyone would think that I was a boy. I hated it. Even though I looked like a boy and acted like a boy, I wasn’t a boy,” Delevingne told Net-A-Porter’s magazine, Porter.

“And when people said [to my parents], ‘Oh, your son is so handsome,’ I would think, how dare you say that! Like, why was I seen as a boy?”

She added: “I always felt pretty weird and different as a kid, and that feeling was something I didn’t understand, or know how to express ... It wasn’t like I was an alien, but I definitely knew there was something weird going on.”

Delevingne, 25, has moved away from her modelling career to focus on acting – her next film is an adaptation of Deborah Moggach’s novel Tulip Fever, and she is filming a TV series for Amazon. She has also written a young adult novel, Mirror, Mirror, drawing on her own feelings of isolation as a teenager. It features a protagonist with alcoholic parents, a biographical nod to her mother’s struggles with drug addiction when she was growing up.

Facebook Twitter Pinterest Cara Delevingne walks the runway in 2016 for Chanel in Paris. Photograph: Pascal Le Segretain/Getty Images

Delevingne has been open in the past about her struggles with mental illness – she had a breakdown aged 15 and was taken out of school – but spoke in greater depth about how the privileged environment she grew up in had not always been so understanding of her depression. “So many of my friends would say, ‘How can you feel like that?’ and, ‘But you’re so lucky,’ and I’d be like, I know, trust me, I know. I know I’m the luckiest girl in the world, I understand all of these things, and I wish I could appreciate it. There is just something dark within me I cannot seem to shake.”

She described how she had been a “late developer”, which had left her vulnerable to the cruelties of other teenagers, who had called her frigid and flat-chested.

“I felt alienated and alone, because I was like: what’s wrong with me? I always wanted people to love me, so I never got angry with them; I turned my anger on to myself. Instead of using [my] sword and shield [to protect myself], I just put my shield up and stabbed myself.

“I hated myself for being depressed, I hated feeling depressed, I hated feeling,” she recalls. “I was very good at disassociating from emotion completely. And all the time I was second-guessing myself, saying something and then hating myself for saying it. I didn’t understand what was happening apart from the fact that I didn’t want to be alive anymore.”

Having been open about her reservations about modelling as a career, Delevingne said that her move into acting had given her more of a sense of purpose, and made her happier within herself than she had ever been.

“Being a teenager can feel like you’re on a rollercoaster to hell, that’s what it honestly felt like to me – but you can get through it,” she added. “Time moves on, feelings pass, it does get better.”