What gives?! Beyond frustrated.

My first day of my last period was August 12. It's September 14 now and still no period. I'm always a 28 day cycle. I'm almost a week late now. Have taken 3 preg test, all negative! My lower back hurts and I'm cramping a bit. Absolutely no blood at all, but I'm having a lot of white discharge. I'm exhausted. Anyone have this happen?