It sounds like you're very frustrated, and it's normal. I'm 22 and still stutter. I'm also working on my own startup, English isn't my native language, and I still get uncomfortable on calls with international clients. One thing I found is that as you keep doing uncomfortable things, you become more 'comfortable' with stuttering. It's something that's 'there' and you just pay less and less attention to it as the years roll on, because shit needs to get done, and you can't hide in your shell forever. There're lots of talented actors, entrepreneurs, and successful individuals who stutter and never let it hold them back. Don't let stutter hold you back.