I see, you're identifying inside as a 6 year old, and your reality is that this part of you hasn't grown up beyond that age, but your body doesn't match because it's too mature, too adult looking. As a result, you feel very uncomfortable in your own skin because your body isn't what you feel it should be, age wise.

I would talk to a therapist about this. I think this could be a result of childhood trauma, or some form of DID, but I could be wrong.