What would YOU do in this complicated situation?

Ok, so I've dated this guy for 5 years (im 20). He has been my everything for that time, my bf n my best friend, the only one I can tell EVERYthing to. He was always faithful n I trusted him. But I was havin issues with his family n I sometimes felt we were more friends, n that we were goin in diff. directions in life so I broke it off just 5 days ago. we were still talkin though n i was teeterin on the edge of goin back. so anyhow, his cousin always has parties at his house n there was one last night. i get there n hes drunk n ALL OVER this girl n its like geez that was fast n of course it HURT! he wouldnt talk to me n was kinda bein mean. then im talkin to this guy whos like "yeh the last party we had he was makin out with some girl!" so i leave n go home cuz i was in shock needless to say. the next mornin he comes to my house to pick up some clothes n i confront him about it n at 1st he denies it then admits to it n said it just got egged on n he was drunk. what to do? i mean this