Frustrated with my OPK results

Kaitlin
I saw my doctor last Tuesday to check and see if I had follicle response after upping my dose from 100mg to 200mg of Clomid. The largest follicle was 16mm and the doctor told me to start using OPKs on Friday and that I should ovulate on Friday or Saturday. 
I tested a day early (Thursday) and had a result that was lighter than the control line but looked promising. But Fridays test was lighter and today's test was barely anything. Did I ovulate already or is my body being cruel? Has anyone else experienced anything similar? My doctor isn't in on weekends so I can't talk to her until Monday.