Implantation bleeding????

So today is supposed to be my last "fertile" day it says only 8% chance.. My husband and I had sex 4 days in a row. The day before my projected ovulation, my "high" day, my peak day, and the day after my peak day which was yesterday at 27% chance of pregnancy. About an hour ago I went to the bathroom and there was some blood.. It was darker than my usual bright red AF and it was pretty light... Could this be implantation bleeding? Would it happen that early? Or is it possible I could just be spotting? Advice/explanation if this has happened to anyone else??? Pleaseee??