I feel the same way. How long has it been going on for you? I've had SA for all of my life. Don't worry, you will get out. We all will. Just don't ever give up. I've been trying to change my way of thinking so I won't care what people think of me. Here are a few things that I have found helpful. Maybe they will help you too.
1) When you're worried about embarrassing yourself, think about whether or not it will really matter in the long run. If you say something stupid, people will probably forget about it within a couple of minutes, and even though at that moment it will feel like torture, after a while, you'll be able to forget about it too. One embarrassing moment probably won't change you life.
2) Remember the good things about yourself. When you are feeling embarrassed, start thinking about the good things about yourself. Think of things that you are really proud of.
3) Look at your situation from someone else's point of view. For example, if you trip on the stairs and you are embarrassed, think about what you would think if someone else tripped on the stairs. You probably wouldn't hate them for it. You would probably just hope they are okay and go on with your life without a second thought about it. That is probably what other people will do too, so don't worry about your mistakes. You're probably the only one who really notices them.
4) You are a good person. If people don't like you, they are stupid, and they can just deal with it. It doesn't matter what stupid people think. They don't care what you think, so why should you care what they think? The nice people in the world will like you, and their opinions are the only ones that matter, because who wants to be friends with a stupid person anyway?
I hope this helps a little. I'll pray for you. Oops here I go again. If you don't belive in God, then ignore that last comment. There that should make up for it right? I don't want to start an argument. We've already got one of those going on...