How to control stutters?

How to control stutters? Hello, I am 14 years of age and in the 9th grade. Recently, I’ve been noticing a stutter in my voice. It’s gotten to the point where I often have to restart a sentence because I can’t get what I’m trying to say out of my mouth. My friends love when I stutter because it often makes jokes that I tell funnier but it has gotten in the way of my reading capabilities in school. Please, I need some advice on how to control it. Help.