Why do you think it is that i really take joy when people hurt or insult me?

for a little bit on who i am, im 17, im starting college this summer im an athlete and an A student... people tell me all the time how wonderful i am, how pretty, how smart. I hate positive attention, i just want to hide. but i really enjoy it when people insult me, call me names, hit me. one of the reasons i love martial arts so much, i love the agressin towards myself. Iv'e hurt myself since i was little in lots of different ways, through cutting, burning and hitting myself. i guess my whole life i have always wished i could just self destruct and die... is there a diagnosable medical condition here? am i normal? is it just normal depression?