What should I do about my situation with this boy?

So, to start this out, I met this guy at wal-mart in the fish section. He walked by one time and I smiled at him. And he told me thats why he came up to me. Anyways, we exchanged cell numbers. Then we started talking. And come to figure out he has a girlfriend. We hang out alot, and when it gets dark things usually get steamy *no sex*. Well, he breaks up with this girl on and off, and he's doing somthing with her this week. So i'm not supposed to text him. He said "I'll text you as soon as I can, don't fall in love with someone else before I can get away from her". So I'm constantly fighting the urge to go see him, and text him. It's agonizing. But I'm totally confused as to what I should do. I know I shouldn't get physical with him due to the fact he has a girlfriend, but I cant help but not when I look into his deep brown eyes. He's what I want, and I feel awful for this other girl, but I can't help it. He's to good. So, please, someone give me some solid advice!