Hi there,
I have had the same problem. I got a few faint lines and then a darker line, but it was never as dark as the control line. My ob says that even a faint line is to be treated as a positive, although the manufacturer's instructions say the opposite.
I got so frustrated that I gave up for this month, but might try again next month given that there are other girls out there experiencing the same - my ob might be right after all?!
I also had a quick look on the internet and other OPK brands recommend to hold your urine for 4 hours before testing - I might try that the next time...
Good luck to us all!!!