I don't want people to know that we have fucked, I don't really know why I care about that.

Once you get past this point, you automatically rise to the next level.

The next next level is not caring who knows who you've been with and you don't think, talk or care about it.

But on to the point, you should take the expeirence, but only if you are forward with her about what you want. And it sounds like you have been partially. You need to tell her up front you don't want anything more than friends with her and don't want to be in a relationship.

If you were very experienced with girls, you shouldn't touch her.

I wouldn't bang her. Just knowing that you can will give you a permanent ego boost when you are gaming other, better girls.

....And, it sounds like you are a kid, and I'm not giving sex advice to kids.

Once you get past this point, you automatically rise to the next level.

so I think if I fuck anyone I can my chances with other girls could decrease.

The easiest way to decrease your chances with women in general is to be more concerned about what other people think of you, than you are of what you think of you.

That said, if you don't find this girl attractive, don't do it.
If you do, then do it.

I don't understand why you bring self respect into this. What's the issue? Extra pounds or not, you still said she's fuckable. How will your self respect drop by fucking someone you apparently find attractive?

Also, I'm scared that if I fuck her she will get really attached and kind of manipulative. She said that if I wouldn't want to meet her more she would get angry, also she started to say that she wanted more then a fuckbuddy (1st time we met!).

Thats your Gut, and its right 80% of the time. She will. So considering this, do you still want to do it?

As far is it affecting your relationships with the hotter girls in the school.. At this point, it was absolutely effect it. Mainly because you're already displaying insecurity about going forward with it and you haven't even done anything yet. Anything you have to do in secret is probably something you have no business doing at all. And if you do whatever that is, there will be consequences.

On the flip side, lets say you say " Fuck.. I Want to bang the chick, Im going to bang her" and you're willing to just own it and not go to far out of your way to hide it you'll be fine. When you accept and live your truth no one can use it against you. Now, that doesn't mean you have to walk the hallways skipping and holding hands with her. Treat her like a fuck buddy, if thats what it is. Explain to her the conditions, and stand by them. Just don't go sneaking around in fear of what someone that doesn't even think about you is going to say.

Life is not about what you do, its all about how you do it. And you're attitude is what will effect your "how". Own your truth and you have nothing to worry about.

Thanks for the reply, good point about that if I'm accepting it people can't use it against me. I think I'll meet her and tell her the conditions, that we are just fwb and that I'm not going to be that available for her. If she agrees I could bang her if I'm feeling it. Or I'll leave and try to stop seeing her if she doesn't agree. She lives really close to me, which can be seen as both a good thing and a problem.