Should I just leave him to deal with her? I'm the rebound aren't i?

i've been in a long distance relationship for almost 3 months now and i haven't got to see him yet but we talk every night. and at first things were good and they still are we get aong great he tells me he loves me and i love him and all that stuff. He is super sweet to me. He is like perfect for me and he says i am to. we click really well. But before we got together he broke up with his gf who he was with over a year and lost his virginity to they were in love big time and planned to get married. she cheated on him with online boys. And he's always saying that he still loves her but doesn't want to be with her and they hung out a few weeks ago and he told me they hugged twice and she leaned on him when they sat on the couch and she didn't want him to leave. He says all these things to me and it seems like he reallly wants to be with me. But i have been nosey and i found his tumblr blog and it has a bunch of stuff about her.. like he wishes she'd talk to him and he loves her more than anything. she means the world to him. pretty much everything he post is about her. and i asked him if he had a tumblr and he was like maybe why? and then he said nah he just likes to browse and listen to people music on there. so he lied.. What should i do? i like him alot and i want to see him and maybe us turn into something he really is a great guy. Why do you think he's so hung up on her still? I am the rebound aren't i? If you were me what would you do?