SO cuming inside me after SEX

Daezhane • 29 years old, Mummy to an angel.. Courtney 30.03.2015 💔🌥
When I have sex with my SO and he cums inside of my my stomach hurts afterwards (like a belly ache) why does his happen???? & we are both STI/STD free and I don't have a urine infection or any cuts inside of me.!! ANY ADVICE ??!