HPT confusion

Kaitlyn

I got a positive on two test on 9/20, and on 9/21 they were definitely there and dark. This morning I used FMU and nothing.. it’s VERY VERY faint as if it’s not there. Should I wait a few hours and test again? Try a different brand? I’ve gotten positives on FRER and then got almost a negative today with FRER.. any ideas as to why I’d get so many positives and then this random negative ?