Need advice.

I've been doing opks for about a week now and last night it was the darkest I've seen it yet. I had egg white cm and ovulation bleeding to boot, but the test line wasn't darker than the control. Tonight I tested and my test line is a bit lighter, I think. Is it possible to ovulate and not have the test line be as dark or darker than the control? I mean it looks almost as dark but still lighter than it says it should be. Opinions ladies? Either way I think I will continue testing to be certain.