OPK help please

Hi all! Okay so I use wofondos and I ALWAYS have a second line. I start testing the day after AF leaves, and continue until around cd 20. I always have the second line. It does get progressively darker and the control matches the test strip around cd 17/18. But I'm wondering if I'm Oing early somehow? This is TTC cycle 3 this month. Really hoping to get a BFP. I am also using preseed, and we are going to bd every other day. Advice?