This kind of stuff happens to me all the time. A while ago, I would try and get them off my back by telling them that I'm gay, which is true, but then it just turns into 'what do you do to her', 'can I watch', crap like that.
Online it's way worse than in real life, too. Don't let it affect your self worth. It says more about him than you. You're not cheap, he's just a pig. I usually just tell them to **** off and continue on with life.