You are probably one of the less popular kids, who didnt get a huge amount of choice in who your friends were. You should make the best of what you have, like your friends are doing, until you leave high school or college or wherever you are and get a chance to make new friends you actually like.
less "popular" kids have stronger friendships...it's the "popular" kids that move in and out of friendships like their own underwear...I teach high school...i pay attention to shit like this, and counceled many
Its you who chooses your friends, don't have friends that you don't like. And it sounds like you lack self confidence as well since you said that you "don't know why they like me either" in which case I would suggest that you find things in life that you can do to make you feel good about yourself but then again the question is vague and i dont really know the situation.
google it and u'll know, am the same