I had this when I was in high school. It controlled my life. I wouldn't go anywhere. I even missed the prom because of it. You're probably dealing with some form of social anxiety.
I didn't want to be like that forever, so in college I forced myself to join some clubs and groups. If I didn't like it I could quit. It wasn't a job or anything. Eventually, I got over it and became somewhat of a social butterfly. It wasn't easy and it took me about two years.
First, I would try volunteering work. If you can't take it, leave! Just try stuff like that. If it doesn't help it might be wise to see a doctor.
You can overcome this.