there is a psychological disorder called social phobia. it can be treated by counsellling, preparation and practice. first you need to know that no body in perfert, in talkign, speaking, pronunciation, walking, eating, listening to others, body, figure, study, knowledge or whatevr. change your perception about yourself, boost your self esteem adn so many things; practice or think or prepare about the topic of the discussion prior to joining study/social groups as mansion suggested, etc. good luck.