9 days late, and all text negative. Help!

I am regular like clock work normally. I've had 4 negative store bought pregnancy tests and today I went to planned parenthood only to get another negative test. Has this ever happened to anyone else only to find out they are actually pregnant.? I want to believe the tests are correct, but then where is my period?? My last cycle was July 21-25th, it's now the 27th of July. I usually run a 26 day cycle. Am I alone in this boat or has this happened to anyone else?