Implantation bleeding (no pic)

I am 10-11 dpo and the spotting started out brown but scant then turned into lighter pink last night, now it's light pink but not enough to even be on the pad. My periods are unmistakable when they happen, really heavy dark flow. I am 13 weeks post partum and wondering if this is implantation bleeding? I ovulated at 18 dpo so this is 2 days before my AF. I have no idea which it is but it is way too light in color and amount.