Late by 11days w/ implanon

<3
I checked it yesterday on day 10 and I'm not pregnant. Will test again around day 20 if still late before going to dr. 
I have been logging my dates with implanon for over 6 months and only ever late 3-5 days. 
But just wondered if anyone has any issues with implanon where it masks anything X 
Tia :)