Don't know if this is in anyway helpful or relevant but I used their opk's for a bit and I'm sure it only happened for the last 3 or 4, but if I dragged them out the bin after around 10-15 mins (like the obsessed woman I am I had what looked like an evaporation line. At the time I was bf and no af so was just playing around with them really but did think to myself "if that were a pg test I'd be retesting in a couple days...". Think you should do a CB digital- when is af due?
I got a positive on a tesco own brand this time around, but had some of these access diagnosis tests in the cupboard, the tesco hpt came up straight away and i thought to myself i will do a couple of these other tests, they came up very faint and took a couple of mins to show up, so i didn't think they were that effective, and the ones i got were the super sensitive ones .
I know it easy for me to say, and i did the exact same thing..but once the time frame has gone, just throw the test in the bin and DON'T look at it again, like i say i did the exact same thing, hoping and praying it would show up pos+. I havehas evap lines before, and it just drives you mad!