I'm 17M and I can relate to this very well. I My advice is make your own little tweaks to how you speak with the help of speech therapy. I mean learning to calm yourself, noticing when you stutter(for example I stutter less when I am with my friends. Probably because I am not thinking about the stuttering and just speak what's in my mind. I do stutter but less), making your own little adjustments to how you speak rather than using just the techniques that is taught in the speech therapy. I am a bit better than what I was before. Remember all the people have problems not just you. They are just better at hiding it.