What you may have is the same that I have which is a stuttering brain. Even when I felt relaxed when I started to speak my vocal cords became tense causing my airflow to be interrupted or stopped resulting in stuttering. I am a speech pathologist and an expert in brain based training. I was able to train my brain to match the brain of a fluent speaker. This was the hardest part of becoming fluent. The brain always wants to return to its comfort level which is stuttering. Nothing worked for me until I was able to convince my brain to rewire itself. Accomplishing this allowed me to become fluent because the brain no longer returned to its comfort level which was stuttering. My brain actually became a fluent brain where I never had a relapse. I am not sure if I could take someone else on this journey. Everything I did was based on the Valsalva response which pointed me to the direction of brain training which happens to be my expertise.