opks can be so frustrating. They're great - but man if they're not ALWAYS some form of a headache.
Also, because this is your first month it might be hard for you to figure out exactly what "your positive" will be. When I was using fr opks, I didn't count it as positive until the control line was darker than the test, because I would always get those at some point. However, other women would never get those results, so to them a positive would be when the control line was equal to the test.
My best recommendation for you is to learn what your positive is, and then to stick with the same brand from month to month..
Of course, maybe you won't need more than one month!