Positives ?

So maybe some of y’all could offer some insight. Last Tuesday I got a positive pregnancy test with first response early result manual. Took a first response digital and it said negative. Went to my doc wed for a beta hcg test. She called to say that day it was 18.1. And that was consistent with three weeks of pregnancy. I have sore tender boobs and bloating. I am two days late for my period. Decided to take another first response digital thinking it would show up and heck it was the last test I had. Anyway it said no - I have an apt with my obgyn Friday since I had a miscarriage in December at 6 weeks. Has anyone else experienced this ? Why wouldn’t the digital register if I’m two days late. And have other positives. Even a positive beta test via blood ???