Clearblue is driving me mad!

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I started taking clearblue digitals on cycle day 7. Low fertility. Cd8 and 9 showed peak! So I've continued to take them as I thought it was an error. So far low fertility but today, cd 15 it went to peak. I'm bd'ing so I think I'm covered but has anyone else had issues with these? Wondering if I should switch to another brand