I’ve been stuttering for almost 13 years, while it’s common in childhood, stuttering into adulthood is almost always permanent from what I’ve been able to research a few years back. Confidence doesn’t do anything to stop stuttering. Stuttering can be a biological issue, such as family history, intellectual disabilities, mental health, brain injury, or lack of speech motor control. These really aren’t anything that the typical human can control, and in fact is difficult to stop. What can help lessen your stutter is speaking slowly, taking a breathe before you talk, and forcing yourself to articulate your speech. That usually helps me lessen my stutter. But since a stutter is a biological issue that can arise from multiple areas there really isn’t anything you can do but lessen it. Do some research and then talk to your parents, inform them on what are the causes of stuttering and how they are things that can’t be forcibly changed on a whim, but require speech therapy and time and practice to work through. Them yelling at you can only make your stutter worse.