How can I get over my awkwardness?

I just feel really awkward when I'm at school. I always think about what I say before I say it, because I don't want to hurt someones feelings by saying the wrong things...so everyone thinks I'm waaaaaay too quiet. I think about every more I make before I preform an action. The only time I can relax and be myself is when I'm playing sports at recess. How can I get over my awkwardness?