Gotcha. You should ask your parents if they're ever known you too stutter or repeat yourself when you were learning to talk or young in general. Thing is - most people have dysfluencies but most people it's so minor you won't notice. Some of us just have a lot more of it unfortunately. I did an intensive speech therapy clinic when I was 13 and that helped me a lot - yet as I was going through puberty I struggled a lot but it decreased as I came into my 20s. I can't diagnose you but if you haven't anything 'big' happen to you, it may just be hormones and teenage stress (no offense). Their is a chance it'll mostly fade over some years, but it may not. You might consider speaking with a guidance counselor to see if your school district has a speech therapist. Speech therapy can help you regain control over your speech if you put in the work.