Trauma is not always proportional to a "wound" inflicted. It's due to a wound going untreated. In my experience, stuttering seems to come from a place where we feel like we have to hold back. When you started, something might have happened that made you decide to not be yourself around others or limit how much of your emotions you're willing to show others. Oftentimes, that tends to happen around 13. The good news is that you there is a lot of hope for you. Contrary to what others have said, the less time you have stuttered, the easier it will be to get rid of it. You need to go see a speech therapist as soon as possible. I wouldn't necessarily suggest a therapist, but try to think of how your life might've changed when you were 13. Best of luck