also, make sure you're taking time for foreplay. the more stimulated you are and the more horny, the more lubed you'll be. i personally find it more comfortable when we have sex less frequently since i also get chaffed. and when i'm chaffed, i'm not as "in the mood" and therefore not as lubed and it's harder for him to get in. KY is cheap and can help. make sure the condom is lubricated as well. play around and see what works for you. for me, a nice thigh massage helps blood flow to the area and can almost always get me in the mood if i'm not too interested.
Try a lube. It's probably nerves not allowing you to enjoy yourself and lube naturally, and it gets worse if you are nervous that "gee it might happen again oh dear is it? oh dear oh no." So, short-circuit all of that self-defeating stuff and just get something like Astroglide and use it and don't worry. However, I WOULD worry if you are having unprotected sex. If that is the case, try a lubricated condom. Take that one seriously, honey, it could mean your health or your life. Good luck! Sex should not be painful.