Opk confusion

Hey girls, I am currently on cd 16. Been taking ovulation tests since cd8 since my periods don't come often and over the paSt few months minus last month I haven't really been ovulating. 
​Over the past few days I have had inconsistent tests... One day it looks like I'll be ovulating in 1 or 2 days time and the next day there is no sign of any LH surge on its way. Anyone have any insight into this and how it works?? Here are a few photos from the past few days.