Opk gets darker?

I was wondering if the test lines on the opk get darker the closer you get to ovulation. I have the biggest fear that maybe I'm not pregnancy yet, because I don't ovulate. I don't know why that's what crosses my mind but it does. I'm on cd 8 so there is a test line, but very faint. So far, that's given me hope, but I'm praying I at least get a positive opk test soon so I can feel like I'm making progress!

So does anyone know if the test line gets darker the closer you get to the big O?