Having trouble staying lubricated?

Okay so when my boyfriend and I have sex, everything is fine and going great for the first few minutes with my natural lubrication. But after a little bit there's a lot more friction and it becomes a lot more painful for me. Even if we have a ton of foreplay before hand. So we started using astroglide lube, and again that works for just about 2 minutes until it's all dry again and painful and we have to stop and re apply over and over and over. I'm not sure why this is.. And we usually just give up because he doesn't want to keep hurting me but I feel terrible that he never gets to finish. Any one else ever experience this? Also, does anyone have any good lube recommendations?