Clearblue digital opks question

Kristy • After ttc for 9 months, we are finally pregnant. 😊 Due April 21, 2016. 💕
I have been using the digital clearblue opks. I typically have 34-42 day cycles. I started using opks on CD 16.  I never got a smiley but when i ejected the stick and looked at the lines every day, they were getting darker and one day the lines looked exactly the same to me. For the past two days the test line has been getting lighter... Could i have missed ovulation? Today is CD 21(highly doubt I ovulated before today but who knows with my crazy cycles).