The hormone oxytocin
released during sexual activity is the cause of the orgasm and the cramps of the uterus
that happen later. Severe cramping may sometimes lead to spotting; yet it is always better to get a specialist guided opinion. I would suggest a physical evaluation by a gynecologist to rule out local causes like erosions, infections, polyps etc for proper management of your condition. A pap smear
and a vaginal swab also would be useful, as is a urinalysis
. Hope your query has been clarified. Take care.