why do I get period cramps after orgasm?

Amanda
Seems to be a running theme in my life that I'm not suppose to have fun in the sex department. 
1st penetration is painful 
Luckily my husband and I found some stretches and things to try that have helped that
2nd and most recent is severe period like cramps after I orgasm.
Very painful and very annoying.
Anyone have any tips or suggestions as how to rectify this?