Youre 13...slow down sweetie!
I agree with Alex (redcar) and David (died.flame) there is plenty of time for sex!
Your body has ways of telling you when its ready for things like sex, dont rush into anything you arent sure you want to do.
Sex isnt something you should take lightly. Not only is it a huge physical step, buts its also a gigantic emotional step.
You need to ask yourself whether or not you truly believe youre ready. Do you know all the risks involved? Pregnancy? Stds? Do you know about protection available to you and your gf? Do you feel comfortable in front of each other? Do you really want your relationship to progress into sex so quickly?
Your first time is something you will probably remember for he rest of your life, dont rush into something you may regret.
We can only give you our opinions and advice, the decision is up to you at the end of it all.
Goodluck with everything!
And as for your penis being 2 inches erect, youre 13 and still growing, you dont have anything to worry about. If you really love and care for each other, it shouldnt matter what size it is.