3days late, brown 'blood', BFN!

[Lollipop1987]

as i recently posted iv been having a few symptoms of what is either pregnancy or the mirena crash....see my post 'Mirena Crash or Pregnancy'. But now at 3 days late for AF i have noticed brown 'blood' when i go to the loo. not a lot but enough to need a liner. iv no pains or anything, slight twinges from time to time in lower adb and that about it. urine test in docs today was neg. i have NEVER had any brown blood/discharge before so im not sure what to think! anyone experienced any of the same?if so what did it turn out to be? afraid if im not PG then theres something else up with me?!!! doctor is very vague, telling me she is there if i need her! just wish AF or BFP would show up so i knew where i was at!