Constant Cramping after Sex?

I'm 39w2days when I went to the doctor Wednesday I wasn't dilated at all still. I had not experienced any cramping or pain at that point either. Well tonight my husband and I had sex and I've had a constant cramping since then. It's been 4 hours and it doesn't come and go or anything it's just like a period cramp. I'm a FTM. Does this mean anything? Or is it normal?