Hi - I am sorry you are feeling this way! I used to have a lot more social anxiety than I do now. I was always worried about what people thought about me, had I said something wrong, etc. Then one day I realized - I'm not on stage - everyone is not sitting back waiting to see what I am going to do or say. We all just kind of do and say what we think at the time - EVERYONE says or does something they feel kind of dumb about later, but to the people who see or hear the "dumb" thing, it is just a fleeting moment. They may think for a second, "that was funny" but they forget about it moments later. Nobody is paying nearly as much attention as we think they are!
The other thing I learned is that whoever you present yourself as is what people believe about you. I grew up in extreme poverty in an extremely dysfunctional family and for a long time, I felt like everyone knew that about me and I walked around feeling ashamed - but you know what? They don't know! No one knows anything about you unless you tell them. And if you decide to go out and act confident, guess what? People will believe that you are confident. Think of the most popular person you know, or just someone you know who is really confident- do they never say anything "dumb"? Are they in any way perfect? Do they never make mistakes? There is no perfect person, and you don't have to be either.
Also, I don't know how you feel about religion, but a lot of churches have great groups for people your age who go on skiing trips together, cookouts and all sorts of fun things, so that would be a great place to meet people as well.
Take care - and don't worry!!!