Faint Positives

I feel every month I get like squinters on my test vvvvvvf lines I don't know why, it drives me crazy and I still don't understand that when ladies test the day before they get nothing and then the next day it's a BFP, I would think they would have a at least a faint, but maybe they don't diagnose it to be faint and just call it a BFN, any ideas, I know  the hormone has to build up but you would think they would get a least a VF line BF their BFP hmmmmmmmmm