If you tell him and he forgives you, you may do it again.
If you were able to make this decision under the influence of alcohol, then I think that's a message from your subconscious telling you how much you value your relationship, otherwise it wouldn't have happened.
Alcohol acts as a truth serum, not a "omg things I wouldn't ever DREAM of doing" serum.
You should tell him. He deserves to know. He'll be mad but if he loves you and wants the relationship to work you guys will work through it. As for how to tell him, do it in person not over a text or whatever. Tell him you're sorry but also understand he may lose trust in you and it will take time to get that trust back.
I am a firm believer that being drunk is no excuse. I'm also a firm believer that if you love someone, you're good to them. Period. So first of all, you should think hard about whether you really "LOVE" your boyfriend. Personally I think that word is typically used too generously. There's nothing beyond love, and if you're cheating on your boyfriend you haven't truly reached a state of "love". So I think you have 2 options: 1: Tell him the truth: It'll be difficult obviously, but just sit him down and say "I got too drunk and made a mistake. I wish I could take it back, but I'll understand if you don't feel like you can trust me, or want to break things off." If he respects himself he will probably leave you. Of course, he may be willing to try to work through it, but it's NOT going to be easy. Your relationship will never be the same, so be prepared for him to have lots of resentments towards you and have little trust in you. 2: OR you could take a risk and keep it to yourself in order to protect him. The problem is if anyone else knows what happens they might tell your boyfriend for you. It's best to tell him yourself rather than letting him find out. He'll feel more betrayed that way. And if he respects himself, again, he will probably leave you.
Of course, this is just my opinion. But I tried to forgive someone for cheating on me and everything beyond that point was basically a nightmare, so be prepared to work hard if he does feel like giving you another chance.Good luck!
I think that if you do love him as much as you say you do then you should tell him, he deserves to know the truth and he should be the one to determine whether you guys will be together forever or not. But expect that he might not want to be with you anymore or might want a break. It would be selfish to keep it a secret. And it's okay to give him time if he needs it, cheating is something serious and if you clear your karma now by telling him, I think you will be fine, and tell him as soon as possible. Remember, if you never tell him, that is going to come back and bite you bad. Good luck with everything, love and light.
Personally being drunk is no excuse. If you really love someone, you would treat them right. Don't keep this secret just so you can keep him, if you really love him you would tell him, you should think about how you actually feel. To me it doesn't seem you are ready for a serious relationship, there is no excuse for cheating on someone, I have been drunk off my a$$ and I still knew what I was doing.Sorry if that sounds rude, I have a difficult time explaining things really.