So it turns out the guy I've been talking to has a gf?

So I met this gorgeous guy at a social dancing night (we're both really serious Latin dancers) right before I went home for the summer and he friended me on FB and messaged me all summer... Now I'm back at school (near where he lives) and I just saw him in person for the first time since at a dance event. He was flirty and charming as always but after I left that night somebody told me he has a girlfriend, who is also a dancer and was there that night!? He's been messaging me almost every day since and I don't know how to feel. I know dancers tend to be a flirtatious bunch but if he was just a cheater looking for a quick hookup why would be message me for 3+ months and be so committed to pursuing me? What does he want from me if he's with her? I've already developed feelings/a friendship with him and I'll be seeing him all the time at dance events so I don't want to do anything to make things awkward, but I want to know what his deal is with his girlfriend. I know I shouldn't get involved, but I can't undo what's already happened and I'm not sure how to handle the situation.