Fuck me! Ok so when I was pregnant with my son I had implantation bleeding and waited 4 days after…

Fuck me! Ok so when I was pregnant with my son I had implantation bleeding and waited 4 days after to test. It came back positive.

So I had implantation bleeding 4 day ago and I tested today and it came back negative. what the fuck! You think it could be because I didn't use the same test? The first time around I used first response and this time around I used some generic brand.