Opks not accurate??

I have a pretty regular cycle. I always get my period every 28-31 days, then get a positive opk around day 14-16. I’ve been TTC for about 10 months now with no luck.

Just wondering if anyone has used opks regularly, thought everything was normal, then found out they weren’t actually ovulating when you thought you were? Or even at all?

I’ve been considering getting an Inito Fertility Monitor that checks the 4 hormones, tells you peak fertility, and then confirms ovulation. But they’re expensive, and I don’t know if I’m being stupid to waste the money when my cycles seem to be pretty standard. Just hoping someone could provide their own experiences, if getting a monitor is a waste, or if I should actually invest in one.