Implantation bleeding?

I had some pink/brown spotting one or so days before my period was expected. It was only when I wiped and was off and on. I experienced this last Friday and Saturday. I thought it was my period starting but AF never came. Tuesday I had a little spotting that was brown and Wednesday I was cramping some in my lower back. I am now 7 days late and no more spotting. I go to the drs Wednesday but I am wondering...if this is implantation bleeding do you count the days from the last day you spotted to take a test or from the first day? I read that you need to wait 6-12 days after implantation to have enough hcg to be detected. I did test on Tuesday and it was negative. Please let me know what you think!