I too, have this "problem". Out of the... well.. many girls ive been with..
4 of them have succeeded in getting me off... i feel your pain. They just dont last as long as the movies and tv portray.
You would think girls would like that.. but they get frustrated. And chapped.
But seriously... not masturbating is the best way... if you have a routine, try to slow it down a bit.. and youll notice a difference. Also, with me, i think its become a mental game. Its all about not thinking about it. That freaks you out and ruins the entire experience.
When i was banging this black girl, all i could think about was the fact that she was black (lol) and i was done in about 15 minutes. Be stupid.