Ok, so you have a stutter. It's a thing most other people don't have. They have an advantage with presentations. But that doesn't mean that you have to be ashamed and try to be something that you are not. Basically you can call it a disability. Why would you shame yourself for having that? Are blind people shaming themselves when they use a service dog? Are deaf people ashamed when they use sign language? Usually not, they just try to make the best with what they have. Tell the teachers that you have a stutter and try to make the best of it. Be kind to yourself please.