Blood test question

I got 4 positive tests, all FMU all FRER, starting from 11DPO onwards. The tests went negative on 15DPO, I immediately got a blood test that day. When I called up my doctors they said my blood test was negative for pregnancy.

The FRER was super faint on that day I got the blood test, but wouldn’t it have still be a positive blood test?

I’m just wondering if these tests were accurate or can your blood test really be negative so quickly after these positives?

These are my tests below.