Positive or chemical?

Today I’m on first day of missed period, and 2x tests today are showing faint lines. I’ve been testing since Friday night with early detection tests - some were fainter than others, but always a constant faint line. Not hugely getting darker each time but today I think so…. I did a urine pregnancy test yesterday at the GP who very firmly within a minute of the sample showed me no positive line, and said - “not pregnant”. So I’ve assumed a chemical pregnancy since I’ve had all these faint lines, but could the HcG levels have been too low one day before missed period? Today I’m feeling cramps. Still sore boobs but less so than a few days ago. What is going on!? My BBT dropped yesterday but is back up high today. Top test - yesterday morning Middle test - this morning Bottom test - this evening