Someone mentioned practising during masturbation. You can essentially do the same muscle excercise any time of the day without anyone knowing. When your doing your homework or whatever, try to tighten the muscles around your dick that u feel when your trying to hold in a piss, and hold them tense as long as u can bare to. (if your still confused, next time your taking a whizz, try and stop pissing mid way)
this will help your staying power a bit, but uve got to be religious about the excercises
With sex though, its more a need to become accustomed. One very basic solution to this which can work well in the long term is using 2 condoms. Heck, use 2 thick condoms, as long as it slightly de-sensitises you, but allows you to maintain an erection. The girl won't mind as it won't affect her pleasure at all, and is infact safer. Whats more is you'll last a lot longer.
After a few times like this, see how you go, when your ready, go down to one condom.
Just think of them like training wheels.
If this fails, have a wank an hour before you see her...
For some people this is just a phase, for others it sticks with them into adulthood, either way if you learn how to please her during foreplay, the you will have sweaty-monkey-jungle-sex no matter how long you last
