Really like this guy but he has a girlfriend? Please help me!?

I met a guy about two months ago on BBM , blackberry messenger. I'm 16, he's 17 and both in the same school. We haven't talked in person because we're both really shy. When we pass in the hall we just stare at each other and smile a bit. He did tell me to go to his locker but I never got the chance as my classes were at the other side of the school, however I am going to talk to him in person really soon. He tells me I'm really lovely and beautiful, we mess a lot and our conversations would go on forever, sometimes about nothing. The thing I really like about this guy is that he is so lovely, quiet and caring. He helped me get over a guy that didn't treat me right a while ago without himself realizing. I felt really happy, the happiest I have ever been even tho it was over text. During this time he had no girlfriend.

He lost his phone about a month ago, we only started talking a few days ago because we got each others BBM pin again. and started going out with his ex, again! She keeps cheating on him but I heard he "loves" her. They have been on and off for about a year, from what I heard she is a really bad girlfriend and I think he deserves better.

The thing is, I really like this guy and I don't know what to do. I don't want to ruin their relationship so I was thinking of waiting until they break up again?

Also, I don't think this guy is one of those users because some of my friends said he's one of the nicest guys you could ever meet.