I have been using Clear Blue Advanced OPK for around 3 years. Got tired of the high fertility but never ovulation recently. I think it only said I was ovulating (peak fertility) 4 times in the past 8 months. I know I ovulate and all my fertility tests (blood work) have come back great. I even started testing the day my period ended just to make sure I wasn’t ovulating early. This got insanely expensive. So, I got on a Amazon and ordered a 50 pack of LH test strips. Got a positive on the test strip today yay! Tested with the Clear Blue just for the heck of it...not fertile. The test strip inside the Clear Blue is even obviously positive. Just a heads up ladies that even the digital OPK make mistakes.