I track my period very closely with a period tracker app. I have a 28 day cycle and I have never even been a day late. I had unprotected sex the week I was fertile (according to the app). I had dark brown spotting for a few days, although I don't remember what days those were. I was supposed to start my period 6 days ago, and so far nothing. I've taken 2 ClearBlue tests, but both have come back negative. What are the odds that I am actually pregnant?