Personality Disorders Support Group
Personality disorders form a class of mental disorders that are characterized by long-lasting rigid patterns of thought and behaviour. Personality disorders are seen by the American Psychiatric Association as an enduring pattern of inner experience and behavior that deviates markedly from the expectations of the culture of the individual who exhibits it.

It's frustrating because you're being seen as something you're not and then you feel you have to expend energy proving them wrong or wondering why you come off that way and why they can't see the real you.
Or maybe that's just me.
But yeah showing different levels of confidence based on how comfortable you are with someone is totally normal. I think some people just have smaller and wider ranges.
Take care