2 days late with negative HPT

Can anyone shed light on this?
I'm a 28 day cycle like clockwork, but I'm two days late.
Taken several tests, all negative. What is going on? This is not like my body at all! 
I wish I could just know one way or the other. 
Has this happened to anyone who has always been very regular? What was the turnout? Preggers or no?