Because of how my family members think of autism, I haven't talk to them about it, nor I will.
Any behavior that could be considered stimming I do when I'm alone. When I'm with others I try to blend as much as possible, albeit unsuccessfully. I try to be spend the least possible time with others because of this, I feel I have to pay attention to every move I make.
This is nearly exactly how I feel, except that I have admitted to rocking as an adult to my family (but only after I was diagnosed with autism), although I would never actually do it in front of them (like you). Have you talked about stimming with anyone in your life, or have you kept it a secret?