Yesterday, I started having brown discharge. It first started off with a clear discharge with a bit of pink in it two days ago. Then yesterday, I had some dark brown discharge with a little bit of blood and then it turned into just brown discharge. All day today, I've been having just light brown discharge. I know that the brown discharge is usually just old blood. But, is it likely that it could be implantation bleeding or my period starting? My period was "due" yesterday according to the app that I use (stopped the pill in August, cycles aren't regular at all) and the last pregnancy test I took 3 days ago was negative.