extreme cramping/nausea post intercourse

This has happened to me twice in the last 3 days now 
The first time it happened, me and my so were having sex, during but towards the end I started not feeling well. I stood up , and felt nauseated, then followed extreme period like cramps but so much worse.  It lasted about 10 minutes . 
It happened to me again tonight , and was so much worse . Still lasted about 10 minutes .. this has never happened to me before. 
Please if anyone has heard of this or experienced this . Tell me wtf is going on either way I'm making a doctors apt tomorrow .