Late?

I am on cycle day 51 of my app no period yet.. I have been off birth control since last November with a lot of regular periods last month or two were off by 2-5 days but nothing like this one.. have taken a few pregnancy tests all negative .. also had a bit of brownish spotting a week or so before original expected period.. now today a tinge when wiping of brownish .. any insights? Doctors urine testing came back negative.. but am going for a blood test next week