From all of the foregoing, especially the title of the thread, it seems that Mike Miller may have pinpointed the primary cause of the problem. Confidence is the key ingredient of performance; if you don't have that then you cannot do justice to any material, no matter how good it may be. Don't waffle for minutes before you cut to the chase, it either bores the crowd senseless of warns them that you're not very sure of yourself. NEVER apologise in advance for any ensuing imperfections, or they will be looking out for them. Tell no-one that you are a novice/student/learner; just get up, smile directly at your audience, and deliver the goods.
Oh, and don't take criticism (or any other aspect of entertainment) too seriously. Have fun. If you're enjoying yourself then chances are the audience is too.