How to get out of my own shell?

All my life I've been painfully shy. I never joined in any groups at school, never took part in gym cl, never went on cl field trips, never ever talked in cl, ignored the teacher when I was called on, etc. I am 31 now, & even more withdrawn, I'm terrified of EVERYTHING...meeting & socializing with people makes me literally sick, even while I'm writing about this I feel like throwing up. I can't relate to people at all. I can express myself when I'm writing, but speaking to anyone, even my boyfriend, makes me come across like an idiot. I stutter, mumble, can't articulate what I'm trying to say. Basically when it comes to other human beings I feel like an alien, like I don't know how to open up, what I'm supposed to say, or act, or who I'm supposed to be. Everyone thinks I'm so weird, & I guess I am, can't even fit into my own species. I went deep into my own shell a long time ago, & now I don't know how to get out.