he's just looking for smome attention
because some guys are just dumb. if I were you I'd stop talking to him before I got even more attracted to him. if a guy is willing to give up his girlfriend for you, what makes you think he won't give you up for some other girl later on?
that same exact thing happened to me! then 2 weeks after him and his girlfriend broke up, he asked me out to dinner.. I basically said no though, cause I'm no rebound.
If you are a caring person, stay away from him; just imagine yourselves his girlfriend and you will understand.