In that case, consider rethinking your use of the word "supposed". Most native speakers from my part of the US will interpret that use to mean something similar to "ostensible".

I.e., if you want to avoid confusion, don't ever say "supposedly X" if you actually do believe "X" is a fact.

Oxford has this to say on supposedly: "used to show that you do not believe that something you have been told is true". Hope that helps