I drunk cheated on my boyfriend what should I do?

We've been together for 5 months now, its a long distance relationship, he went away for college and we see each other on vacations (winter break and summer). I've already had a problem with hooking up and alcohol in the past, so I don't drink much anymore, especially now that I have a boyfriend. Drinking turns me into this weird party animal version of myself and I don't like it, it caused me too many problems already. To be honest I've been the perfect girlfriend until this, this past five months I pretty much avoided going out to stay and FaceTime him, but yesterday it was my best friend's birthday and I had to go. I had way too many margaritas, I was so drunk and I just wanted to get home. The weird thing is that I had no trouble curving a guy that came on to me at the party but then a friend (who lives near my dept) offered to take me home. And I said yes because I didn't want to drive in my condition and it wasn't like I was going to be alone there with him (because he has a chauffeur). I remember taking the stairs to my floor, the guy was with me holding my bag, he helped me unlock my door, I waved him goodbye, thanked him and went straight to my room to lay down. I thought he left but then I remember seeing him entering my room, he didn't say a word he just crawled into my bed and started kissing me, I can't remember exactly what we did just parts of it but I know we had sex. When I woke up he was laying there naked and I didn't know what to do, he promised not to tell anyone and I believe him (he hooked up with a friend and never told anyone, I know it because she told me). Plus I know him, and he doesn't do that kind of stuff. I feel terrible, I don't know what to do? What do you think? Should I tell him?
I drunk cheated on my boyfriend what should I do?
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