My boyfriend is on the Brink of Breaking up with me over something stupid!!!?

Ok...so About 3 weeks ago I cheated on my boyfriend...I didn't go all the way with that other person, but we did fool around....It was one of his brothers in the same fraternity as him...so OF course he found out...but anywho..we broke up and he took me back like three days later..and of course he doesn't trust me..so now,He has threatened to break up with me because I went to a party back home with a friend, and she recorded it and I won't show him the video...I didn't do anything else with anyone else, but I did act like an idiot b/c I was drunk and he already thinks that I am "IMMATURE" ...so I definatly don't want him to see it, b/c then he may think even less of me, and he did tell me that if I continued acting stupid while he wasn't around that he would break up with me.....so either road I take is going to crush me because I really do love him ...and I just don't know what to do about this situation...I mean I can't show him the video...but if I don't then what????? Please help!