OK, so you know everything works right, this is perfectly normal. Many of us have been there and had that same thing happen. Being your first, her whatever, its natural that you'd be so focused on "doing it right" that nerves probably played a big role in this. Also the environment wasn't really good for something this important and that too probably played some role in your losing the erection. DON'T get too worked up over this....that'll only make things worse. This sorta thing happens to all of us at some time, yes it is embarassing, frustrating and leaves you "in need" of a release. Take some time, talk with your girl about this and try again when things are better. Use lots of foreplay and be sure to keep a condom handy! Remember that your two heads are VERY connected and can play very bad tricks on you. Take it easy, nothing is wrong that can't be fixed with a little work. Sex really requires that two people are very in tune and it usually takes some practice for everything to be totally OK. I know what you head tells you.....that you oughta be perfect the first time...and that simply is NOT true. Keep in touch and we'll help you through this....you're not alone!