I think you are too shy and lack self confidence because of that. You should try to increase the occassions that you must do anything in front of people. You just need practice, always drop your shoulders, breathe slow and deep, relax your facial muscles, and look at people softly. Be prepared for your tests and first practice speaking about a subject in private. Sort of like acting lessons to a mirror. Have fun with that and then move on to having people test you from a set of flash cards you have made up concerning different subjects.