Ok, I've been hooking up with this guy for a little over a month now. He has a girlfriend, and I'm usually not into guys, just something new and fun for me, so the relationship is purely sexual. When we get together, everything is going great until we try to actually do the deed. He can get me off with his hand and I can blow him no problem. But if we try to actually have sex he loses his erection. Wtf? What's happening? Is he just not attracted to me? When it happens he gets super pissed and starts apologizing. The thing is I know for a fact this isn't happening with his gf because sometimes I can here them having sex. So am I the problem?