I like him but I don't know if he likes me back?

Well if you guys have talked about liking each other before then it should not be a problem. You should find a time when he has nothing to do and just hang out with him. Tell him how you feel (tell him he seems like he is uninterested in you lately and you want to know if your relationship will ever progress) and then see what he says. If he apologizes or seems like he feels bad for you ever thinking or feeling that, then he probably likes you. If he acts like it's not a big deal then he probably doesn't. He may be too busy for a relationship.