Positive OPK ?

Rebecca

So I had a positive OPK yesterday morning, my first positive ever in the 7 months I have been taking them!!!

But I took one lastnignt around 10 and It was very clearly a negative .

Thoughts on why this happened ? I have been crampy so I think I’m ovulating. But is it normal for LH to drop that fast ?

These are the ones I took yesterday morning .