Opk showing no lines

Hi everyone how many of you have actually tried opk and got pregnant with its help. This is my 6th month ttc and this process has started to get me. This time I started opk on 8th day of my cycle but till 11 th it showed me blank like literally no faint lines nothing...and on 11 th day I have good amount of cervical mucus ...egg white watery . Now I am starting to think if it go by opk or by my body indications through CM. I usually ovulate on 14th-16th day. Please help