13 days past missed AF.. Advice?

I am 13 days past when I was supposed to have AF. All test have been a bfn. I started spotting three days ago. I've only been spotting in the mornings and just about a quarter size on a pad and just when I wipe in the morning. The spotting is brownish pink and j had a little red blood. Usually my AF is heavy and never more than a day late. What could this mean? This is our first month TTC and I am 13 days late. Any advise is VERY much appreciated!! 😍