There are soooooooooooooo many other ways to please a woman besides penetration & if she absolutely must have penetration to be fulfilled then I would go with Oz's comment & use a toy or strap on.

My only other advice is to think of something else while you're going at it. Baseball, riding a bike, taking a run, whatever... concentrating on controlling your breathing I've read also helps quite a bit too.

Best wishes!