My grandad who is also a severe stutterer got his PhD from Cornell. He was nervous about it but he said he just plowed through anyway. He also went back to speech therapy when he started college, which he said helped a little bit. He said it was often embarrassing but that if the worst that will happen is being embarrassed it wasn't worth not accomplishing the things he wanted with his life. I can tell you as a teenager it's still pretty hard to follow that advice and live that way. Almost impossible. Anyway, he still does presentations at conferences and teaches and things like that, and still stutters a ton.