Drunk.

[Lonely-Reject]

Basically, I went to my (female) friends 16th birthday on Saturday, and I got a little drunk. By little I mean I was quite drunk.
I'm really quite sure that I am straight, but I started making out with her like accidentally, and touching her up and stuff. Then because it was a sleepover thing, putting it simply, I fingered her. But now the few people who were there think that I really am a lesbian, including my best mate :/
I don't know how I'm supposed to convince them when I did that :/
But even though I did that I regret it and am certain that I'm not bi :/
And I just want to be able to get my friends to see that :/
So how can I convince them that I really am straight?

[Invert]

There's no way to 'convince' someone you are straight. Like even if you go have sex with 100 men, that's not proof. I think it might be important to take your friend aside this happened with, and explain to her you were drunk (we all do silly things when we are drunk). And tell you friends in general, that regardless of what they think of your sexuality, you identify as straight, you consider it as something you did when very drunk, and maybe experimenting, and although you can't prove you don't like girls, you dont have to, they should still respect your opinion. At the end of the day, if they think you are bi, you still know you aren't. It may blow over soon. A lot of straight girls have had sex with other girls, particularly in their teens.

[Maiden]

I agree with what Invert said. You can't convince them. Just tell them you're not and let it go. Don't make a big fuss out of it. They'll probably keep going on at you just to tease you and because they know it's making you react. Just say you're straight and then change the topic if it comes up. They'll soon get bored of it.