negative test no period? what?!?

So today my period is due and usually glow is accurate when I get it. But I didn't get my period and yesterday I took a pregnancy test and it came back negative! What the heck is going on?? It's freakin me out. I was getting my period every month ever since I got off birth control so I knew I was getting my regular periods and during the same time. If I got a negative test then I'm not sure what could be happening!!