OPK Question

This is my first month using OPKs and I'm really confused. I've been testing since CD 9 and it's currently CD 19 and I still haven't gotten a positive. I take a test about 4 times a day, in the morning, at lunch, when I get home from work, and before I go to bed. The darkest one I've gotten so far was today at 11:30 (see picture) Does this mean I'm close?