How long do you get faint BFPs

[mummof1]

I'm 99.9 % sure I'm suffering a chemical .. My positives were very strong last week and even yesterday when I was bleeding .
Today very faint on first response .. Negative digital .
I had a blood test today I'm wondering if it's going to come back positive even though I'm most likely not pregnant anymore .. How long will it take for the hormones to be gone ?

 

[Rei]

I'm not sure about chemicals but I completed my miscarriage about 4 weeks ago and I was 13 weeks pregnant. I am still getting very faint bfps. So it might take a while.