I'm so sorry your father treats you like that! Your stutter does not make you any less worthwhile and purposeful than any other person on this planet. It's not your fault you have a stutter, and while I'm not sure what could help you cope with your situation, I did wanna say that you should not feel bad for stuttering. It's not something you can control and your dad of all people should be able to understand that and be patient. His actions are not your fault. Anyways, I hope you get through this and things get better for you somehow