I feel like such a dunce, but as I've never have a positive OPK I'm curious. I'm using bulk test strips I got on Amazon. So does the test line get darker and darker and then after ovulation get lighter and lighter or does the test line just not show up anymore? I'm frustrated because I'm testing twice a day and midday the test line was darker than the evening test. Today's midday test was similar to yesterday's. I'm CD12.