There is no such medicines that can prevent sweating. As u said u r lacking in confidence, n getting nervous. yr basic personalty must be of shy nature .u may not have more friends looks like u may be interovert. Only u can help yr self by making more friends n talk with them open up with them, speak with them on any subject loudly n clearly. this will help create more confidence in u.This is some kind of fear complex. this can go away once u start mixing with more people n making more friends.