I thought that I was pregnant I was having all the signs I took a test on the 17 my period was due on the 15. It came back negative. Then on the 21 I was at work and I had really bad cramps, I almost passed out from the pain. Then a couple of hours later I started what I thought was my period but there wasn't a lot of blood, just mostly blood clots. This stopped early on the 22. I still feel kind of sick.

Maybe you were pregnant but your body couldn't handle it so you had a miscarriage. You should go see your doctor. It could have been something more serious.