Tmi! Cramps after orgasm?

I'm 8 weeks pregnant, our baby is healthy & growing right on track, but since about 5 weeks when I orgasm, I get painful cramps in my uterus that last about 5-10 minutes. I've read conflicting info about whether these cramps are harmful or safe, and I definitely don't want to do something that could cause miscarriage or something. Anyone experience this or know for sure whether it is safe or not?