an uncomfortable feeling

i need help... almost every time me and my boyfriend have sex, i start to hurt afterward. like id either start to feel sore or burn right away or id feel sore or burn when hes trying to go for round two... which is like 10 to 15 minutes after round one. I went to my obgyn and my doctor to get tested for everything and they come back clean. I dont have an std or anything worth worrying about. so I'm wondering what should I do