I'm CD15 today and have been using OPKs since CD10, as I have no idea when I ovulate, this was my first month trying OPKs to try and work out my cycle a little. So on Sunday, the test line wasn't quite as dark as the control line, but I thought it wasn't for off, and that I was probably due a positive in the next few days. So I do an Opk this morning and there is barely a line in the test box. I was expecting to have a positive test as Sundays looked so close, So now I'm very conconfused.