It seems that a pattern is repeating itself with regards to the kinds of people that your dating online. I've noticed the same (albeit a different pattern, to yours) in my relationships. It might be partly attributable to the signals that you give off, possibly unconsciously.

Regarding this particular guy, I think that in some respects he is trying to be honest with you, about his issues. Or perhaps, by explaining how he feels, he's hoping to be able to understand his own feelings. He sounds very conflicted. However I agree with other posters; this relationship is unlikely to work out, also he's probably raising the topic of sex because he wants to try to persuade you to give him your virginity. Him believing that you have nothing in common is a very bad sign in my view; even if you believe it to be untrue.