Possible cryptic??

So my last period was 10/20/2019 I ovulated on 11/02/2019... I only had sex once on 11/02/2019 unprotected. I started testing 11/08/2019...I know early but I was stressed about it... I went from negative stark white to faint positives and on 11/13/2019 I started spotting 11/14 I had a medium to light flow and tested and had a negative... 11/15 I had flow medium to light and the same for 11/16...by 11/17 I was spotting and had nothing on 11/18 on the night of 11/18 I felt a really bad headache and all day 11/19 wouldn’t go away I tested and bam full blown positive... I went to the docs and they told me it was negative and sent me for an hcg qualitative blood test on 11/23 my result came back <2 and 11/25 the same <2 so that means negative I’m still having these symptoms of dizziness and nausea and I tested again and I’m still getting a line I’m due for my next period 12/09/2019 could there be a possibility that I am pregnant but not building hcg??? Has this happened to anyone before? If so what did it end up being?