So last month I didn't use OPKs. But this month I'm back with it and using the Tesco OPKs. I'm CD 19 today (31 day cycle?) and I think I have my positive. I don't have any more OPKs at home to test again, but I'm confused slightly. Half the test line is as dark as the control in my eyes lol, the other half is faded? Or perhaps this is just as dark as it gets?