Ovulation Microscope HELP NEEDED

I just wondered if anyone could help me. I am using an ovulation microscope to track OV at the moment and every morning i do what i am meant to and leave it 15-30 mins to dry then look at it. Yesterday and the day before it was crystalized after half hour but when i checked it in the afternoon it was definite ferning patterns. I showed numerous people (they think i am using it to check if i OV which is kind of true and not to TTC) Last night i checked and the whole lens was covered in ferning patters which looked amazing but in the morning it was crystalized. We BD'ed anyway but i can't find any answers on google and i don't know where else to go.

I did a saliva sample this morning and it is crystalized again but i could bet that tonight it will show ferning patterns again. I have been having OV pains and sore boobs so i am pretty sure the ferning is correct but why doesn't it show up for a few hours????