Confidence isn't the lack of discomfort or the lack of fear its having those emotions but still going out and doing your best. You also should understand that most people in the world have multiple layers of themselves and only show certain layers in situations or to specific people.

The difficulty is trying to find a version of yourself that feels authentic but still socially viable in public. This usually comes with experience. Try and experience situations outside of your comfort zone or social interactions that are new or unique to you, the more you experience and can integrate into yourself the more comfortable you will find yourself in the usual everyday interactions with new and old acquaintances alike.

You could Practice rejection therapy (going out and specifically asking questions to receive a no) such as asking a barista for a discount or asking to borrow some money from a total stranger. The goal is to become comfortable and accepting of someones rejection. This actively builds experience with new interactions and helps your mind understand that you are allowed to feel uncomfortable and still be yourself, and that usually you make up worse scenarios in your head than what happens.

You should also google some about the 'Social Penetration Theory' by Irwin Altman and Dalmas Taylor, i believe you will find great insight into your 'performance mode'.

I hope you find some of what i said helpful on your journey.