Why am i such a jerk to him?

i know i definitely feel something for him, there's a lot of emotion. But im not sure if i hate him, or if i just care way to much for him. Whenever i see him happy it makes me feel bad. Like i honestly don't like seeing him having fun especially with other girls. But then he's like that with me too, whenever im having a good day, and im having fun with all my friends, he'll be off to the side acting all emo. and im pretty sure its because of me because the only time he,s not like that is when im quiet and not doing much, or if im not even around! and then i love having fun around him, just to make him feel bad, like seriously i'll be acting more silly and just rubbing it in. and i really think it makes him unhappy, im just a jerk, i know it am! lol oh btw i guess you should know me and this guy have had this really messed up relationship for a really long time, some days we'll be totally touchy and lovey dovey, and others we completely ignore each other. it makes me mad. and now lately i haven't been reacting or doing anything to him when he gets playfull . and now that ive stopped doing anything is when we've started making each other mad or whatever. ughh so i guess what im asking is whats wrong with us? whats wrong with me? what should i do? :S