Does he like me back?

These are always tough questions to answer since it's hard to really know what's going on inside the guys head. I would say that the way you guys talked all the time that he does or used to like you. As for what happened, could be anyone's clue. He could be dating a girl, he could have given up on you thinking you didn't like him. He could have gotten some bad advice like give you space and make you pursue him. The best thing to do, would to be sit down for some coffee and talk to him, and find out. If you're open and honest, even though it's difficult, you will find the answers you're looking for, either good or bad. But at least you could put your mind to rest.