Ladies who have gotten pregnant with no positive opk?

Last month I got a positive opk on cycle day 13. So I imagined I ovulated on day 14. Didn't get pregnant unfortunately... this month I have been testing since day 11. However the line has gotten lighter and lighter and lighter. I am now on day 16 with still no positive opk. I read that it's not that common to miss a month of ovulation unless there are some other health related issues going on which I don't believe I have... maybe O is just really late but I felt like the OPKs were strange by getting lighter instead of darker... I don't want to be out for the month already 😫