I Made a Mistake

I cheated on a girl Ive been with for a little over a year now. I had cheated on her once before and had thought it best if she just didn't find out, and she never did. I cheated again on new years, the second and last time. I was at a party and got completely trashed, and this girl who went with my group and I hooked up. I was so trashed I did not really think about who was watching and if it would get back to my girlfriend. I told people I was on a break with my current girlfriend, which i was... she just wasn't aware of what break meant to me. That night I called my girlfriend to tell her we needed to break up. I told her I would much rather not hurt her by cheating on, and that I thought it was best if we broke up. It completely crushed her, not to mention the fact I did this on New years. I feel like a coward and a liar ( two things I know i am ). She never deserved what I did even though i had asked to be on a break. And now past all of that... when i go back to school I am apparently going to get the beat down of my life. I'm not afraid of being hurt, its just a sad thought so many people don't like me, i feel like i am alone. I told my girl friend what happened and she just cried. It broke my heart, but I think I did what was right by breaking up with her. I have no idea what my next steps should be. The girl I cheated with and I are probably going to date, but I think that will just make my life worse. I don't know what to do...