Pain and cramping during sex

Been with my bf for a year and about 6 months in I developed pain and cramping during sex. They build up while he is thrusting and get worse and worse. Like the worst cramps I have every experienced. Unable to move afterwards, curled up in the fetus position waiting for them to fade away. Some positions are better than others but it happens often no matter the position. Even if he slows down or doesn't go as deep it still hurts.

I don't think it's dick size. he isn't the biggest I've been with. My ex was a lot bigger and wider but it never hurt (but was shit sex but tmi 🤣)

Any advice? Experienced this before? Should I see a doctor?