Implantation bleeding after BFP

[Isit2021yetplease]

Hi all,
I got an unexpected BFP last Thursday. we had had unprotected sex a couple of weeks before but I thought I had already ovulated a few days before (and had had quite a bit of wine - not the best time to make judgement calls...)
Anyway I woke Thurs morning with tender boobs and I just knew. My period wasn't due until saturday but I got a first response early detection test and it clearly showed positive.

Very late friday night (about when period would be due) I had some very very pale pink staining on tissue on wiping, a bit more the next day, then a bit of dark red old blood, but nothing more.

I first thought chemical pregnancy (which I've had before) but my tests are still positive and I've had nothing further.
My question is - i thought implantation bleeding came before you got a BFP as it was the implantation which caused the release of the hormones picked up by the test?

Has anyone else had bfp then implantation bleeding?

The egg implants for some time, we normally call implantation the moment it attaches but it kinda burrows it's was in over a period of a week or so which is why people often report cramps around the time af is due so I guess in theory this can be why sone people get a small amount of bleeding after they've had a positive test as the egg continues to disrupt the womb lining. I guess if it stays light it probably was implantation bit of it gets heavier it could be a chemical, good luck xx

I had implantation bleeding at about 6 weeks, 2 wks after BFP