I'm supposed to get my period this upcoming Friday but got what I think is implantation bleeding this Friday. I'm a week early and I usually don't get my period early ever. The blood is dark

Brown/black. I've had implantation bleeding with a pregnancy in the past but it was after my late period not before so I'm kind of confused. I had sex during ovulation but I was on my birth control (my last pregnancy i was on BC too) I took a test the same day the bleeding started , so far

It's negative. I'm having cramps and it isn't just spotting but it's not heavy either