Period or implantation bleeding?

So about 4 days before I was supposed to get my period, I got super light bleeding for about a day and then just brown spotting for another 3 days. Not normal for me. I am now 6 days late from when my period was supposed to be. I have gotten a few BFNs, but I have not tested for a few days now. I have had nausea, fatigue and back pain almost daily since the bleeding happened. My question is, do I keep testing and assume it was implantation bleeding or do I count that as my period and move on?