Whats wrong with my boyfriend?

I met my boyfriend in July & we were so happy & nothing could serperate us and he warned me that he has a short-temper but little things just piss him off & he starts fights with me like he told me that if I leave him that he'd kill himself. But he has had mental break downs lately...I mean last week he dumped me bcuz of one he had then he asked me out the next day...last nite on the phone he was being dumb and he started a fight w/ me then he started yellng at me & then he told me he didnt care about me then when I yelled I'VE BEEN MAKING MYSELF PUKE!!! he totally freaked out & said please don't do this to yourself honey...I love you...I care about you..then he was really pissy ..then he was really pissy today & ignoring for his friends and then at lunch time he was hugging me and telling how great I am & how pretty I look. then he was holding my hand when school ended.it is like he mood swings...one minute he is happy and the next minute he is pissy.What should I do?