Obsessive guy friend please hel?

i became friends with this guy in like april and we were just good friends and talked all the time and told each other everything. were still really close but now hes just obsessive. he gets mad at me every time i evenm look at another guy. if i'm with another guy he threatens to wreck my life. he calls me non stop and it's just getting scary. we fight all the time yet we always become friends again. for some reason i don't like when were not friends but i can't figure out why. i hate him yet i still wanna be friends with him? i try so hard to break things off yet i always end up talking to him. i just don't know how to stay committed to it. can someone please tell me what to do because if i donn't do something soon i'm scared something bads gonna happen, he already threatend suicide