Adrian Derbyshire, who shared photos of his dying daughter Julia in hospital to raise awareness, said abuse began after she spoke about her sexuality.
Instead of celebrating her 18th birthday last week, “I ended up putting roses on her grave”, he said.
He said there should be more education in school about online bullying.
“I wouldn’t want any other parent to go through what I am going through at the moment,” Mr Derbyshire, from Warrington, Cheshire, told the BBC.
Speaking on BBC Radio 4’s Today programme he said the bullying started after Julia, then aged 13 and living in the US state of Missouri, spoke to a friend about her sexuality and the friend told the school.
The teenager was abused physically, psychologically and online, he said, and she returned to the UK to live with her father in the last two years of her life.
He said she developed mental health problems from the bullying and she returned to the websites and the forums where the bullying had taken place.
Mr Derbyshire said he has spoken to more than 200,000 children in the last two years about his experience.
But, he said, he wanted to “up the ante” by posting the photos on what would have been Julia’s 18th birthday and “provide something that would shock them, to make them sit up, to make people talk at the kitchen table and so we can kind of get this awareness out there a little bit more”.
“It was a very difficult decision to take the picture, never mind to release it,” he said.
“It’s been on my phone for the past 16 months just buried in there.”