Orgasm in my dreams- then horrible cramps?

Lately I have been having dreams where I am having sex and I orgasm. Right when I orgasm I wake up with horrible cramps- almost worse than my menstrual cramps. My back aches,  I usually have a bowel movement, and I almost feel like puking. I woke up like this 3 time yesterday early morning and now again this morning. And the pain usually goes away after bout 10 minutes!  Anyone had this happen? Is it normal or should I be worried? I'm expecting my period in the next week or so.