I have the ovulation strips (from Baby4you) and I chart also.
My cycles are all over the place so can easily use 10 a cycle so that's why I went with the cheaper strips.
I'm not sure if it's just my body, but I've never had a true positive result and was testing at 4pm each day like you're supposed to.
I read on Fertility Friend that a lot of their fertility specialists have told them to test with their 1st urine of the day and have had much better results. I'm going to do that next cycle and see how I get on.
Good luck to you