Excruciating Pain and cramping after sex

Sometimes I get a terrible cramping in my cervix or lower abdomen after I finish having sex with my boyfriend. The pain is similar to period cramps but also like a cramp you get before diarrhea. The cramping usually passes in about 5-20 minutes. The pain is very intense and the last time it happened I broke out in a cold sweat and was nauseous. I've talked to my gynecologist and she just wanted me to pay attention to when it happens (before periods, when I need to use the bathroom) but there is no pattern. This has never happened with a previous partner. Help me! Any one experience this too? Any suggestions of what this may be? I was misdiagnosed with endometriosis at 18 but later was told I did not have it. Help!