Implantation Bleeding at 13dpo?

Hey ladies... So question for you! Is implantation bleeding possible at 13dpo? I'm having some...tmi alert... dark brown discharge, just a little bit, that started today. AF is due tomorrow but I've never had this kind of start to my period. It's always full on red and lots of it at the start. I've also had some mild cramping starting late last night as well. I'm just confused and wondering if anyone else has been in this boat and what their outcome was for that cycle BFN or BFP?? This is my second cycle trying for baby #2 and I didn't have spotting with my first at all.