Ovulation cd20

Claire 🌸
Hi all, very first post.... I have been using OPK's for the fifth time this month. Since cd 11 I have been getting faint positives... I'm now CD 20 and still not had a big positive! I'm genuinely confused. We BD unprotected Thursday and Friday as I thought my ovulation day was only a day or two away. How have I still not ovulated?