4 days late and bfn

I've been pretty regular for almost a whole year of AF coming every 28 days. I took two tests here at work about 2 hours ago, 1 urine and 1 blood (I work at a hospital) and both negative. When I would use the bathroom today and wipe very light pink that was barely visible would be on the paper. Not sure what to think. Something just felt different this month and I thought maybe this is it...guess not. Sorry for the rant