All my OPK testers...am I normal?

Cj • Unexplained infertility. IVF mama of 👧👧

I’ve been checking OPK 6 months now.

Month 1 I ovulated on CD 13

Month 2-CD 14

Month 3-CD 13

Month 4-CD 13

Month 5 CD 15

month 6 I’m on CD 16 today and still getting negative OPK. I am getting close according to CM but even if I get positive tmw I’ll be on CD 18 before I ovulate. Is it normal to vary this much?