Period 8 days late!

My period was supposed to start March 1st and I'm still waiting. All my tests have been negative and this is starting to drive me nuts. Has anyone else kept getting negative test and ended up pregnant. When I was pregnant before it took forever for me to show up with a positive test, but I knew I was pregnant then so I'm wondering if it's doing the same thing this time. Although it was 15 years ago when I was pregnant so I'm not sure. My periods were irregular during my first few years of high school, and I got on birth control shortly after that. I got off of it for a little while and then back on when I met my husband at 19. Since then I've been on the pill for about 11 years and just recently stopped November 2015. I had a period December 31st, and my second period was January 30th. I am concerned that maybe my cycle is not regular but I have been regular for the past two months. Really confused and trying not to stress😑😯