Confused with OPK

I'm on my last and final round (3) of Clomid at 100mg and doing everything I can to get a BFP. I haven't been doing OPKs because I thought I knew when I was ovulating...well I guess I was wrong. I'm 2 days earlier than I thought, although it doesn't seem like a lot I know it can make a huge difference. Iv tried OPKs in the past and always used digitals but SO bought the ones with lines instead and I'm a little confused. Yesterday I got lines that were very dark and today a little bit lighter, so I thought yesterday was Ovulation day, but when I update my GLOW it says its today. Is this correct?? When is more effective to BD? Yesterday when I got the dark lines and my % showed higher or today since it shows ovulation days even though my lines are a little lighter?