stupid boyfriend troubles

i know its stupid and trivial and not that important but i just need to vent a little.

my boyfriend is getting rediculous. he flirts with other girls in my face, and ignores me for them. he promised me he would talk to the girl he broke up with me for, and i found out recently that hes been talking to her for 4 months. he constantly lies and breaks promises and makes me cry on an almost daily basis. he also yells at me when we get in fights and it scares me.(those who know me know how hard it is to scare me)
i can't break up with him though. im miserable with him but im worse without him. like he promised hed call me today cause hes upstate for 10 days and he didnt. im not mad cause he lied, im mad that i didnt get to talk to him.
its so messed up. i dont know what to do. ive tried talking to him and it hasnt worked its just pissed him off. what should i do?