I have been using Opk sticks from Amazon for past few months now. I know my cycles are 40days so think I ovulate around cd20. This month I think I may have ovulated on cd 15 bc I had a line almost as dark as the control line on opk. Dtd just incase but just a bit confused. Going to Dtd each day until next week just incase. Just going crazy. Don't get what I'm doing anymore. Been trying for 10 months and think I'm doing something wrong. Going mad. Advice needed please!