Has this ever happened to you? What does it mean?

I am 13 dpo. I started getting dark brown discharge (light/spotting) at 11 dpo, still experiencing it now. I have taken test and all negative. I wear a pad but it is bright white, it's only there when I wipe. No smell either. I know it's old blood, but I'm supposed to start my period tomorrow, just have never spotted 3 days before...does that make sense?