Issues with PTs?

Has anyone ever had issues getting a possative test? Maybe it took you way longer then "normal" to get that pretty pink line to finally show up? I know some people get a possative before they even miss a period but has anyone ever had to wait like weeks after their missed period to get a possative? With my first I couldn't test possative on a home test at all. I had to see a doctor to get a possative result. Anyone else?