I'm going to scoot this over to Women's Sexual Health
So is it the begining part of sex that hurts (penis entering) or the end part? Is the pain towards the opening of your vagina or towards the back. Have you ever experienced bleeding after/during sex? Do you get cramps when you have sex?
Does the pain go away after you shift positions a little and does it hurt most when he enters all the way?
It sounds like he's hitting your cervix or even an ovary. It hurts like crazy</>, but it's fairly easy to avoid if you're careful. I'm not saying he's rough with you, but certain positions can be painful for some women no matter how gentle the man is. The easy way to fix this is by remembering and avoiding any painful position you were in, sometimes it's just a matter of shifting your hips. Make sure your guy is aware of where it hurts so he can remember to either avoid the position as well, or remember not to thrust in the entire way when you're like that.
I also saw that you are having lubrication problems, and that can makes things pretty painful as well.