I can't imagine what you are going through as it must be very traumatic and overwhelming for you. As you may already know, sudden onset at your age is pretty rare, but I guess the silver lining is you have an educated idea why it is happening to you. The singing without blocks is a common thing. My best advice is when you have to give a presentation, etc, think about disclosing the fact that you stutter in the beginning. It can lift that weight off your shoulders and help you get through it. I dont know what the doctors think re: temporary vs permanent, but if the stutter is something prolonged you may want to seek out a speech therapist. Lastly, dont lose your confidence. Even with your stutter, you are still a skilled, experienced, powerful public speaker. If you have any other questions or just need to vent feel free to drop me a line!