Dry sex

Me and my boyfriend has sex today. I performed oral on him, I love doin it, it turns me on, turns him on. We switch and he performs oral on me, im lovin it, so he then gets on top of me n apon entering I felt a little pain like I was completely dry. We had sex n after I asked if he thought I felt dry n he said a lil bit. Idk wats wrong, im completely turned on by him, I love him but I was dry. My period went off the day before completely, would that b a reason?