I guess this is what truly makes everyones stutter different cuz growing up i always had a mild stutter throughout elementary,middle school, and high school but i also was going to speech therapy at elementary school like almost everyday. It was therapy provided by the school tho. Sometimes i wonder if that kept my stutter mild throughout my teen years. It wasn't until I turn about 17 or 18 where i had an incident where someone pointed out my mild stutter as a joke where I started blocking immediately after. i guess cuz it made me more aware of my stutter and more controlling it. Another thing I'll say is to the op 13 year old , dont let someone make fun of your stutter as its not something to ever be ashamed about as its not your fault so own it. As for as overcoming it thats hard as im currently stuttering bad til this day. Growing up speech therapy in school did okay for me. Another thing read books everyday to yourself, make it a hobby. Goodluck