He probley doesn't hate you. It seems like he likes you
I'm not really attractive and I'm not popular either , but this one boy teases me a lot (he is one of those cool guys too). Does he like me or does he just hate me? Sometimes it seems like he does it to make me mad.. so what should I do?
No I don't think he hates you, usually if a guy teases you he likes you.
He probably doesn't hate you. I mean if a guy really hated a girl, they'd probably either ignore her or make her life a living hell. I don't think teasing counts as either of those.
Since he's once of those "popular" guys, I would assume that he's an extrovert who probably likes to joke around with other people. (Correct me if I'm wrong). If so, then it most likely means that he likes you as just a friend to goof off with. I wouldn't think much of it except for that.
If he's one of those rare introvert "popular" guys, then he probably either likes you as a friend or "likes you likes you". I wouldn't get my hopes up on this just yet because those "popular" guys are coveted by many girls and he doesn't seem to be showing any signs that he actually likes you that way since you are questioning whether he likes you or hates you (if you catch my drift here). I'm not saying that it's not possible, just saying that it isn't easy. But you never know.
If this guy is bothering you with all the teasing, you need to tell him how you feel. Don't let him get away with something you don't like just because you aren't "popular" and he "is". Stuff like that don't actually matter when it comes to basic human rights of feeling comfortable in your environment. Actually, they hardly should matter at all, which is why I always out popular under quotes.
Anyway, hope this gives you an idea of what you might be dealing with here.