OPK conundrum

Lucy
Ok, I'm getting a bit confused about this whole OPK testing... I have been testing for two weeks. I finally started to get a darker test line over the past few days. I figured I was getting close to ovulating (glow also says I will the 24). I thought I would try the clear blue advanced digital starting today. 
Now, here is what I am confused about... the digital blue advanced reading states, "I am low fertility" but when I look at the stick it is clearly the same colored/darkness lines.. and the cheaper sticks show I am getting close... so would that make the clear blue wrong? 
I'm very unsure of these tests. I know I need to start doing body temps, but I guess I'm trying to just get situated with doing one thing before confusing myself with another... any help would be so much appreciated!! 
Pictures are attached of the tests.