What went wrong? (what happens next...)

I ended up talking to him again. I couldn't really resist for long, since i still felt that tinge of interest in him. Ever since then, which is now about 5 months, i talked to him every Friday and Saturday night. We'd stay up texting each other until we'd crash, which would be at like 3 am. I honestly thought he was starting to fall for me, just as i fell for him. He told me things about himself that he hadn't told anyone else. In return, i told him things that i had kept to myself for so long. The only thing that kept me from believing that he liked me was that off and on relationship he had with that girl, his girlfriend. Shes much older than he is, and doesn't seem to be as friendly as him, or so Ive heard. Shes more of a troubled girl, and despite me not knowing her personally, i know she does not treat him the way he should be treated. I never want to bring up the conversation of why he even likes her to begin with. I guess he just does. What hurts me the most is that although she constantly hurts him, hes still with her. Thats pretty much it from then. They are still together, and I'm just the dumb 2nd choice when shes not there. I just hope that some day i can be more than that. That one day, he will realize that i was always there for him when she wasn't. But until then i have to deal with the lousy truth that he doesn't feel the same about me as i do about him. And that haunts me everyday.