Its not my fault?

Alright, it is time for some tough love.

First, you are under 18 and don't need to be getting drunk. It never helped anything!

Second, why are you hanging out at your ex girlfriend's house and getting drunk anyway? I thought your question was going to lead to you having had sex with her. Which again leads me to - don't get drunk! have your wits about you!

Did your girlfriend know that you were hanging out with your ex prior to you calling her for a ride? I would just venture a guess that the first girl only jumped on you when the girlfriend was coming just to mess with her and make her jealous. Either that or maybe you were flirting and she wanted this girl to know she better watch out? You'll have to tell us.

Anyway, it is your fault. Own up to it. This is why it is your fault:

You were at your ex girlfriend house (friend or no friend - she is an ex girlfriend - a no! no!)
You got drunk (therefore putting yourself in a predicament)
You called your new girlfriend to pick you at at the ex girlfriend's house (don't you have more friends?)
You allowed the 2 girls in the room together - the whole episode of new girl seeing old girl on top of you (just dumb - still not sure why this girl thought she should/could get away with that?)

So - you made the decisions that lead up to your girlfriend thinking you were cheating on her. You are young, START MAKING BETTER DECISIONS! Don't go where you don't need to be, don't get drunk (have I mentioned that before?) and don't put yourself in these situations all together and then try to not accept responsibility.

The best you could do now is a heartful apology to the girlfriend, a promise to never be in any type of predicament like this again and then following it up with more intelligent choices in the future. Don't know if she'll buy it or not. But anyway - you should have learned a good lesson here.I hope!

If you didn't cheat on her and what you have said is true, the only thing you can really do now, is (like I said before) to talk to her.

When she saw you two together, it would have been a big shock to her and she would have been very very upset. By you making her even more upset and getting angry with her, she's going to think that you got angry because you're guilty.

Sit her down and say "please, just listen to me for a minute." and then explain what happened. I'm not enitrely sure she'll believe you though. I don't think I'd believe this story if my boyfriend told me this.

If she has questions, answer them truthfully.

If she's upset, undestand why.

Put yourself in her shoes, if you saw what she saw - her kissing her ex boyfriend after a drunken night together, would you take you back?

The only thing you can try is to talk to her, if this doesn't work, give her some space and try again. But if she really doesn't want anything to do with you after this point, I don't think there's anything more you can do.

Firstly, why are you going round to your ex's to drink excessive amounts when you're taken? You seriously think this was a good idea in the first place especially when your girlfriend isn't there?!

It's just out of bounds to go round to your ex's house when you're in a relationship with someone else, you're asking for trouble.

It's all a bit strange to me, you get drunk at your ex's and then suddenly she jumps on you randomly? Hmm. I think I'd be suspicious too if I were your girlfriend, I mean, let's face it, so far you haven't given her much reason to trust her, have you?

"Somehow we got in a fight" Is the "somehow" there because you don't want to tell us the specified reason because you're trying to seem like you did nothing wrong or is it that you made her cry or because you can't remember because you were too drunk?

You should NEVER get drunk at your ex's house, you probably shouldn't even be there if you're with someone else.

I think if you really want your girlfriend back, you should try and sit her down and talk to her and try to explain it without getting angry. She's done nothing wrong in all this so do NOT get angry with her. If she feels upset or angry, she's allowed to because clearly it's a very difficult ordeal for her. You getting into a fight with her and making her cry really won't have helped the situation. So listen to what she has to say, stay calm and maybe she'll give you another chance, but to be honest from what you have said, it's not looking good.

If you get her back, do NOT go round to an ex's house. ESPECIALLY not for drinks and getting "wasted".

well , I f you care about your new girlfriend, stop hanging around with the old one, its disrespectful to your girlfriend, and the other girl just wants to cause shit

Yeah man, I don't think, after that incident, you should hang out with you ex anymore, unless you really don't care about your current relationship.