Maybe you could make her come before you enter
and use a condom when you do. That way you will last longer
and she will have her pleasure as well.
You could also try some different positions. Some positions (I don't have my book here, so if you want I can get the list in a week or so) give significantly less "pleasure" to the man, making him last longer.
And you could also try to have sex twice on an evening. It is commonly known that a man lasts longer the second time.