One in four 11 to 18-year-olds have received a 'sext' by phone
A worrying number of teenagers are swapping or being bullied into "sexting" or sending intimate photos on their mobiles, police and a children's charity have warned.
One former "sexter" said she almost left school when a photo she sent her ex-boyfriend ended up in the wrong hands.
Helen, not her real name, told Newsbeat she was 14 when she sent a series of topless photos to her 15-year-old boyfriend.
"He had just threatened to dump me and said if I took them we could get back together," she said.
"I made him promise he'd keep them to himself. It took him about two weeks to convince me - he was constantly pounding 'please please' - he said he needed them for us to be together... and at the time I decided it would be an OK thing to do."
People would stop me in the street and recognise me. They called me a
A week later, Helen said a girl at school showed her a photo and asked if it was her.
"I was absolutely mortified, horrified," she said.
"Everyone had seen them, not only all the people in my class but even at other schools in the area. The pictures were up in the bathrooms, in the corridors.
"People would stop me in the street and recognise me. They called me a porn star. I couldn't go to pubs, it was embarrassing for my friends as much as me."
Helen said it got so bad she contemplated leaving school.
"I was going to leave school at one point but I was too mortified to explain why to my parents."
According to charity Beatbullying, one in four 11 to 18-year-olds have received a "sext" on their mobile or by email.
The charity warned girls are often bullied into taking, and sharing, explicit pictures of themselves.
When you are young and have your first boyfriend, all you want is for the relationship to work. You'll do anything to make that happen
Helen said she thinks she was an "easy target".
"I thought if I did it for him, everything would be happy as larry and we'd be a happy couple. Obviously that didn't happen. I was a bit naive at the time, I was only 14 years old.
"When you are young and have your first boyfriend, all you want is for the relationship to work. You'll do anything to make that happen."
Helen said "sexting" by email was the "worst way to do it".
She said: "He just thought it would be funny to spread them around everywhere. He sent them to one person, they passed them on and that's how it happens.
"It can become different things, it got to the point people were drawing on them, putting naked men next to them," she said.
"The more people saw it, the more people played with it, the more people enjoyed making a mockery of me."
It's just not worth it. Even if you are with someone who is completely reliable and you honestly don't think they'd do that, you just never know
The Child Exploitation and Online Protection Centre (Ceop) says it receives daily reports of harassment or blackmail after private photos or "sexts" have been lost or circulated.
Some "sexts" have ended up on forums used by child sex offenders, it has warned.
Helen said she no longer talked to her ex-boyfriend: "After that I had no relationship with him.
"I don't think it was always the idea. He was very good friends with a girl in the year above me who I never got on with. Either he showed them to her or she found them.
"The way it worked out wasn't intentional, but things like that happen.
'Just say no'
"He obviously feels really bad and whenever he sees me he still comes straight over and apologises.
"It's been a bad thing for both people. He lost friends because it was a nasty thing to do somebody and it absolutely mortified me."
But Helen said she never considered going to the police or talking to teachers at her school.
"I didn't think it was big enough to go to the police, I was embarrassed, I wanted to ignore it."
Helen said she would tell anyone who is feeling pressured to send a "sext" to "just say no".
"It's just not worth it. Even if you are with someone who is completely reliable and you honestly don't think they'd do that, you just never know.
"Nowadays with the internet, it goes around so quickly, it's better to stay away from it than risk getting hurt.
"I don't think anyone who does it is 'a kind of person like that' but people make small decisions in a small amount of time.
"The repercussions are big. For something so small as taking a photo for someone. It's not worth the heartache."