how to be a 100% self confident in public

when i have to go out, i tend to be very ' on edge' and nervous because of my anxiety condition and ptsd...i tend to become unnerved and aggravated very easily by being around people, and loud noises especially unnerve me.

all i want is self confidence, self belief and to not doubt myself at the drop of a hat.

i go gymnasium a couple times a week to swim, in order to feel better in mind and body.. what else can i do?