Seconding propranolol from my experience. I'm both a clutterer and a graduate speech therapist and I have it prescribed specifically for "speech anxiety." It truly helps me! I actually have two clients who have moderate/severe stuttering and I've wondered if it would help them (but I can't say anything about it to them). I, thankfully, haven't had any adverse side effects from it. Xanax helps my fluency as well, but it makes me drowsy. I have that for mental+physical anxiety and propranolol for only physical anxiety (like before giving a presentation in class).