I know exactly the feeling. Most people don't even know that I stutter as it only emerges on more anxious situations. Last month I had an interview through video conference and it was a total disaster, all I wanted was it to end. Later I've got a call telling me that they liked me and my resume and that my stutter was not a problem at all. I literally could not believe, I even asked if they got the right number and name. So what I got to tell is don't be so hard on yourself, try to view these situation that you described as opportunities to practice your speech (easier said than done, I know), go see a speech therapist if you can, if anxiety is your problem, work on that too and try to always be on your best shape (well rested, workout, eat healthy, breathing and mouth exercises, etc.).