OK. Then you're not gender fluid. What's the problem? Are you saying if you're not gender fluid nobody else can be? Are you saying you need a name for what you are? Pick one. Make one up. Just be sure it's an adjective and not a noun -- because (as I say too much) these things should describe you, not define you. You should never put yourself in the position of saying "I have to do <X> because I'm <Y>."
Perhaps you'd prefer "gender presentation fluid?" Your inner self is constant, but your external presentation can change according to your feelings?