Spotting or early AF?

For the last six months or so, before I'm expecting AF, I started spotting, I think, its lighter and pink/brown but sometimes black (which I read is 'old' blood) sorry for the TMI! But it'll be from 2-4 which is almost a whole other period for me! And then I'll just have 1-2 regular flow days that always start on Day28, I can't figure what's causing this spotting, or if it really is spotting or I've become irregular? First month I was elated thinking it might be implantation bleeding (we've been TTC for almost three years now), anyone else had this??