you may have social phobia.
i.e. a kind of anxiety related to socializing with people.
You need to learn relaxation techniques and then social skills in a guided manner. Most importantly is to start with a small group. Build up confidence that you can interact with people in a relatively relaxed way. Do it slowly, don't force yourself. i.e. don't be self-judging of your performance. Just participate more without thinking and without a particular goal or intention.