I can no longer be on top because of that. We have had to switch to other positions. It's pretty much try and see until you find one most comfy for you. We find doggy style is comfy. I kneel on the edge of the bed (box spring & mattress so it's about the height of his stuff) I put a pillow to support my tummy and I find its the most relaxing and comfy. No cramps yet. I'm 26 weeks with twins.
I would have sex too and get cramps and a lot. Try and find a position that you like and where it wont hurt.. plus the semen can make you get cramps also
The position you do can be putting pressure on ur belly try not to lay on your back for long periods. Your partners weight can cause discomfort. . It did for me anyways