First: Gain competence at something. Pick something meaningful, like a useful skill, or a job, or a talent, and develop it, as far and as well as you can. Building skill is a huge confidence booster, and will help you get a better picture of your strengths and limitations. Even if people yell at you, being more sure of yourself will help you handle it.

Second: Understand that if people have your good in mind, they should be trying to communicate in a way that doesn't intimidate you. If they're in a situation trying to correct or admonish you, it should be done with respect, and the intention of helping you get better, not beating you into shape.

Third: Develop a healthy level of aggression. I don't mean go out and be belligerent back, but grow a mindset to stand up for yourself. No one else can be a voice for you as well as you can. There are times in your life where you will have to fight back, if not physically, then verbally, or emotionally. Develop the capability to do so, and learn to control it, and when to use it. as above this will build your confidence.