Chemical or whhhaat the hell???

Sooo I got a bfp 3 days ago and my tests continued to get darker yesterday and then this morning it was much lighter and the digi test said “not pregnant” (that was the first digi I’ve taken) ☹️ Since then, I’ve taken two dollar store tests that showed negative. Should I assume it’s a chemical? No bleeding but have been cramping for the last couple weeks and my boobs are crazy sore. Period was due today but so far that hoe hasn’t shown up and I’m never late and never cramp.