Wondfo opk...confused

Julia • Trying for #3
I usually get a positive opk around cd12-14...I did have one time where I had it at cd16 but idk i check it morning noon and night. I know it's getting stronger but it's really pissing me off...has anyone ever had their ovulation late before? I have a 27/28 day cycle normal cycle I believe...ugh...9 months and it's getting frustrating..