I am 3 days late with my period-never late-and I've been cramping since two days after ovulation. I had unprotected sex two days before ovulation. The cramps come and go sometimes with nausea but they only stay a minute or so regardless. Ive taken several tests-all deffinetly negative-and other than being tired and crampy no other symptoms. The cramps dont feel like a 'just starting' period. Its more like a 'ending soon' period. Any idea what's going on?