Last month I tried OPKs but didn't start til CD16 and CD17 - both were negative so thought maybe I had left my testing too late.
This month I used an OPK on CD10,12 and 13 (today being 13).
I went off the pill at 4.5 months ago and my cycle length has been 28 days for the past 3 months.
I'm using Clearblue OPKs so I thought they would be quite reliable. Should I be worried?