I feel you hv Fear of Failure or Rejection  which stops you  subconsciously in facing the people and crowd. Do not worry.  If u can consult a Psychologist in your city and share with them all the events and situations I am sure you can overcome this issue without any difficulty.

I would like to say what you feel is one of the most common behavior known as fear of public speaking. Few tips to control and eliminate it. Do light exercise before you enter in to discussion it will reduce your anxiety levels. Practice your speech in front of mirror while observing your gestures and body language feel free to change them to your optimum influence/comfort level. While presentation keep your focus on the contents of talk rather than audience reactions and Practice your talks in front of some friends or family members before you present it on a larger platform. Well, you only require to follow these tips for the time until you found yourself comfortable with public presentations than you will gradually develop your own personal style for successful speeches.