Last month my first day of my period was on the 10th. I usually expect my periods between the 8th-10th. I had cramping as if I was going to start around the 9th but nothing started. It is now the 20th and have had no sign of a period lately. I have taken 4 pregnancy tests and they were all negative. What is going on?! I have NEVER missed a period and I have not been under any stress - everything is the same as it has been for years. Is it possible I could be pregnant, even with all these negative tests?