There is a version of you that exists only when nobody is watching. Not a secret self — nothing so dramatic. Just the one who does not adjust.
Most of us perform constantly and gently: slightly funnier in one group, slightly more serious in another, slightly more certain than we feel in a meeting. This is not dishonesty. It is social competence, and a person without any of it is exhausting.
The trouble starts when the performance stops switching off — when you find yourself curating an evening alone, or choosing a book partly for how it would look if someone asked.
A small test: what would you do this evening if you knew with certainty that you would never be able to mention it to anyone?
Whatever comes to mind is worth paying attention to. It is the closest thing you have to a direct answer.

