I've heard that the blue dye tests are no good. Does the store you go to have anymore red dye tests? You could always order a digi on line.....it would take a couple days to get to you, but if you want positive confirmation it might be worth it. Or could you go to your doc for a blood test?
I think a positive is a positive even if it's light. I don't know what it means if it gets lighter from a darker positive the day before. Keeping my fingers crossed for you!
G + D = M