OPK for those not trying to get pregnant?

I am currently not on any bc and I only use condoms. I’ve talked to my gyno about using ovulation tests to predict ovulation and avoid having sex then. So that’s what I did.

I started testing on day 11 and my ovulation peak was on day 16, so I didn’t have sex till day 19,20 because I know that ovulation can occur 24-48 hours after ovulation peak. On day 20 my ovulation was low.

Can I use this method every month or it’s not reliable? And ofc even when I am not ovulating I am always using condoms+pull out+water tests afterwards and I am being very careful. I just want to test my ovulation to ease my mind because i don’t want to risk and have sex on my ovulation day because I now plan b doesn’t work when you are ovulating