nah man ur straight... i had this problem before (just about every guy proilly has once in his life, honestly, over some kind of issue)... you just need to be comfortable and you'll start off slowly and then have absoltely no problem ever gettin it up.... it's hard cuz you know its all in your head but once it happens ur like WTF? just relax is all i can tell you, dont even think about it..... just make the motions and then put it in and wallah ur good p/o man (oh ya and if the girl ur gonna have sex with is on the pill that's a plus, condoms can really be a pain in the ass with thie problem)
Don't take offence in some of the comments.
Their just playing with you..
I think your nervous too, just like djufo said!!
I wouldn't worry about the sex thing. Just be with the girl and when the time is right it will happen.
Just for your info. It happened with a guy I was with (he was 35)!