I learned this a while ago... Dont try and please people... I learned that i dont care what people care about me... Just go into it with that mindset, and you can say anything you want without fearing you'll be judged..
i have a friend who is like that to.... try to be very social and if at school you are worried about getting an answer wrong just know that everyone makes mistakes and its humanly impossible to be perfect.
It's all about mind set. You think your a horrible speaker, but in reality, you're just not trying. Before you speak, take a deep breath imagine the worst thing that could happen (I imagine that the zombie apocalypse will come from my awful speech), and laugh at how stupid you're being.