OPKs? Why all negatives?

Shayna
So, I've been testing with opks everyday for 7 days now. I started at the beginning of my fertile window according to glow... also the same day the box said to start given my cycle length. I've gotten all negatives and I think they are getting even lighter now. First pic is from 2 days ago, 2nd pic is from today. Any advice?? :(