Is thr any medical reason why i get so very nervous during public speaking while most people are only moderately nervous? is there any cure for this?

Performance Anxiety : A beta blocker - type of blood pressure / heart rate medication - is used by solo musicians, public speakers, and actors to help with anxiety associated with their performance. See your local doctor and give it a try. With more speaches, more experience and more expertise on your material you can train yourself to lessen the anxiety during your performance.