The realization you cannot do the simplest thing such as reading out loud creates blocks. According to my personal experience, when you'll start read you need immediately at any cost say as many words as you will be able to until you'll get a block. It will set a certain tone for your performance and give you confidence (I think you agree that just getting a block will be much worse, including for your well-being). During the reading, contrary to the advice 'don't think about it, etc.' focus as much as it possible on the text, take control of yourself, speak in a ringing voice from the beginning and don't leave the line, don't leave the space in your thoughts for stuttering, don't stop for a second, even if you get a block, the most you can do is awkwardly finish your speech for a long time, taking a lot of time away from the audience, or until someone'll stop you. Good luck to you, I know how hard it is. Of course, things I've written in previous paragraph are close to impossible. If you don't want everyone to know about your speech defects, just avoid these stressful situations. In this area you can come up with something on your own. It will be much easier (if, of course, you have the ability to do so).