Should I trust the first response or dollar test

Hey everyone.

I’m posting because I’m having issues.

3 days ago I took 3 first response pregnancy tests on the day of my missed period, all 3 came back positive instantaneously. I went to a clinic in my town who offer free sonograms but you have to take their cheap $1 pregnancy tests. I took theirs and well, it came back negative. And I instantly went and bought another FR test that came back instantly positive. I haven’t been pregnant in over 3 years and am honestly just in shock that I am.

My last period was September 21st and lasted about 3-4 days. (Shorter than normal) which would put me at 4 week pregnant.

Should I trust that these tests are more accurate than the cheap ones?