Isn't it unusual to to get menstrual-like cramps and some bleeding after orgasm?

Not the ususal: Orgasm can cause the uterus to contract and if there is anything inside (polyps or fibroids) it could cause bleeding. It would probably take a sonogram or sometimes a small scope inserted into uterus thru cervix called a hysteroscope to determine that. Obviously make sure you are sure you are caught up on your pap and get checked for infection if that is a possibility. Less likely hormonal.