There are several tests that Speech Therapists use to diagnose and determine severity of a stutter. Among them are speech samples, which you wouldn’t be trained to do right now given your age and education level, and there are resources like the Overall Assessment of the Speaker’s Experience of Stuttering (OASES) and Stuttering Severity Instrument. Assuming you live in the United States, your school Speech Therapist will be able to access both of those and more. I can tell you that a stutter “going away,” or what Speech Therapists call “spontaneous recovery,” becomes less and less likely the longer you’ve had it, and from 5 to 13 is one I’d personally assume wasn’t going away. I suppose it’s technically possible, given how the brain tends to restructure during puberty, but I wouldn’t count on it. If you’re having these feelings about it, find an adult you trust, whether it’s your parents or a teacher, and explain it to them. Among them, they should be able to get you connected with someone trained to handle stuttering, whether at your school or an outside clinic.