False positive opk?

Hi all!

My husband and I have been ttc for 4 months. I almost always ovulate on CD 21 and I always have fertile cm during ovulation week and a positive opk. This cycle I started temping and I got a temp dip yesterday and a positive opk this morning, but its only CD 16 and I have absolutely no fertile cm. In fact, I don' think I have really any cm at all. Could this be a false positive or if I am ovulating can I still conceive even with barely any cm? For ladies who do not produce lots of cm during fertile window, do you have any tips to still conceive during ovulation? I'm just a little confused and wondering if any ladies on here have experienced this before.

Thank you in advance!