It looks positive but why did I get a diff reading using clear blue ?

These Wondfo tests are from 3/16/17 - 3/21/17 (this morning). This morning test on other apps & from other woman say that it looks positive but than a few hours after taking the last Wondfo test I took a ClearBlue Digital test & it came back low?
I thought it would at least say high fertility (blinking smiley face) but was shocked to see low.
Once I get home tonight from both my jobs should I test again with Wondfo & see if it looks darker or lighter? Could it have been a bad test? Could I have already ovulated? Or could I be ovulating in the next couple days?
I only started using tests a couple months ago with not much luck so any insight, help, suggestions, etc. would be very helpful.
Thanks


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