FMU & OPKS

I use Wondfo OPK. I read online that some people use FMU/SMU on Wondfos and get a true Pos and some dont get a Pos at all. So I want to ask you ladies if you can use FMU/SMU? Also do you use FMU/SMU and get a true Pos?  I am on CD 12 and still havent gotten Pos. My avg AF is 26d but this past AF was 20d(came early for some reason)