I have been using OPK's for the past 5-6 days..I started early. My last AF was August 9th. I get AF every 28 days, which means I should be due September 6th. I *should* O around August 23rd....Problem is...my opk's have been getting lighter, not darker

Today's OPK line I could barely see ..
(baby-ment)
I started using OPK's this month because for the past 4 months, I have not really noticed the physical signs of O, even though AF comes every 28 days....I never had a problem with O before giving birth....I don't BF either..
Opinions? I am at a loss..