I need help

Paige

So, Monday the opk was kinda dark. But they're dried now so it's hard to tell. Tuesday they got lighter so I figured I already ovulated. Today its dark again! Glow is predicting me to ovulate tomorrow but last month I ovulated a few days early. What do yall think? Why would they get lighter and then dark again? I'm pretty routine with my cycles and dont have any problems.