I use an app on my phone called My Days to keep track of the days I have been intimate and when I have my periods... My last period was March 20th, and according to the prediction on My Days, I should have started my period on the 17th of this month, I am now 8 days late and I have never missed a period before. I have taken two pregnancy tests though and both were negative... is it because I took them too early? Or am I in the safe zone for not being pregnant?