OPK after Follicle check

Leslie Clare

Went for a follicle check in the AM in cd 13. Dr said things looked great (3 mature follicles) and I should be ovulating soon. He told me to start taking OPKs that night. My OPK on cd13 at night was close to positive but it has gotten lighter each day. Today, cd 19 it’s barely there. What day do you think I ovulated on?