I messed around at a party and am asking for forgiveness

You've already done it, you've proved to him that he means that much to you, his girlfriend and his best mate that you would do that behind his back.

You've taken the trust from the two people in his life who people mean the most to him.

I hope he does the right thing and f***s the both of you off.

You've ruined his friendship with his best mate and you for what? A little bit of noggey? Sums you up in a nutshell don't it love

Well you broke the trust and to make it worse you did it with his best friend, so yeah that's not good, if I had a girlfriend and she messed around with my best friend oh man there would be hell to pay on both their parts, first I would ask what the hell were you thinking to her, and then to him I prob wouldn't be his friend anymore. That's going to take some time for him to get over if he ever does, he might or he might not. The thing to do would be give your boyfriend some time to think about this and its understandable that he doesn't want anything to do with you right now.

explain how you didn't mean it, softly. he's angry. very. but just remind him how everyone makes mistakes that it seems that other people don't understand, and you are in that spot. ask him to understand, you never meant to hurt him. you made a mistake. so does everyone. good luck.

Make sure to never do it again, honestly if I was him I wouldn't talk to either of you ever again.

Tons of good advice already here from other answers. I can only think of some edge-case tangents to add to the discussion:

1. Likely your "accidentally" (which you've already been taken to task for) is hindering your boyfriends acceptance of your apology. Stop saying that not only to yourself, but also make sure you say the opposite to your boyfriend (thus, accountability. ) He needs you to change, to have learned from this, to care about him and your relationship in a way to didn't care before your "accident. " Without that, there's no hope. With that there is a chance he'll try again. But you need to demonstrate new trustworthiness to him.
2. He might NOT ever want to try again. You blew it and can't fix it in this case. But you can learn and change in exactly the same way as above, so that you don't go and hurt your NEXT boyfriend in the same way.
3. If your boyfriend DOES come back to you, don't let him punish and mistreat you for what you did. He did lose trust. He does feel insecure. Or sad. Or resentful. Or plenty of negative things now. But you don't deserve to be hurt by him over this or anything else you've done wrong. Obviously, that means physical. But it also means, if he uses this to yell at you or call you names, that's wrong of him too.

That said, he'll need to say SOMETHING negative about it if you get back together. But there's a big difference between your boyfriends saying "I'm angry. I trusted you. How could you do that? Now I don't like thinking about making out with you. " and so on. VS "You're a slut. You don't get to go out with your friends without me now. Shut the f**k up! "

Accidentally? Thats a lie. You can lie to your boyfriend, but not to logic. You cheated on him, that is very, very wrong. He didn't do anything wrong, and you betrayed his trust, of course he wants nothing to do with you. That was a very selfish act. Especially with his best friend no less. Your young and you need to learn from this experience. Just because you want to be forgiven doesn't mean he'll do it. You f***ed up. Deal with it.

Take it from me please, a man whom has been down this road, with deep regrets. Take ownership, admit it, and move on. Don't get caught up in name calling, or back stabbing, just remain friendly, kind, and make yourself more fun, by forgiving yourself. You learned a lesson, so just like school, move on and don't do it again.

Just let him break up with you. Your lucky you still talk to him.

Learn from your mistakes and move on.

That is something really hard to get over.
Put yourself in his shoes,
Would you like to be in a relationship with someone who completely broke your trust?

Or hop back into your shoes and ask yourself
Would you like to be in a relationship with someone you cheated on and who might possibly hold it against you the rest of your life?

what you did was not an accident. the sooner you stop lying to yourself the sooner you'll figure out who you really are and what you really want out of life.

How the f*** can you ACCIDENTALLY mess around?

You don't deserve him.

thats silly. things like this always happen when you underage, how immature of his best friend to makeout with you? and you too. no offense hehe. but if I had a caring boyfriend I would be with him and nobody else!

So what ever came of this scenario anyways? Did he forgive you, or did you both move on?

If you were drunk you may have not been thinking clearly, but if your in a serious relationship, drinking can't be used as an excuse for messing around, you should know better even under the influence. If you weren't drunk it was also NO ACCIDENT, perhaps he kissed you first. But you didn't stop it, Would you forgive YOUR boyfriend if the roles were reversed? I didn't think so.

I really think you weren't thinking before you "made out" with his best friend. Yes it is hard to forgive a girl. I did similar to my "boyfriend" but I didn't make out with anyone. He eventually forgave me. It's not the apology, it's him actually gaining your trust again.

It's no accident but I don't know what to tell you now, but what if he had done that to you? I don't think you'd be able to forgive him, right?

First of all - How do you "accidentally" make out? You have to be aware of and acountable for your actions - Especialy when it affects someone else. You cheated on him then you deserve whatever attitude he wants to give you!