Positive OPK on last day of fertile cervical fluid?

We’ve been TTC for 8 cycles. My husband is a truck driver so it’s HARD to do the deed more than once or twice per fertile window. But I’m wondering if possibly we have been missing the majority of my window. My OPKs are usually positive on the last day of fertile cervical fluid, (even turning into non fertile fluid). If a positive opk means ovulation is coming, I’m confused as to why my cervical fluid changes so quickly. I usually have a very quick peak on my opk before returning to baseline.

Anyone have the same thing? I have an appt with an OBGYN but it’s not until October. This month we had sex the day before my positive opk and the day of. I’m hoping we covered our bases.