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?

Edited: I didn’t mention that this was a chemical and my period came days after my tests went negative... I just was wondering how my blood test was negative on the day I still got a very faint positive and the day after I had a positive test?

These are my tests below.