The problems you are facing could be due to normal shyness/personality (depending on your age), or a problems called social anxiety
(where you face a lot of stress
in talking in front of people etc) or general anxiety etc.
I would suggest you speak to a psychiatrist
who can do a proper assessment to arrive at a correct "label" to your problmes.
Both medication and "talking therapies"-(counselling
to a kind of psychotherapy
called CBT) may be used to help you overcome the problem, if there is a diagnosable psychological problem.
But, one most important thing is that YOU NEED TO MAKE AN EFFORT, THOUGH IN SMALL STEPS, TO SPEAK OUT, (even though you may have lot of anxiety about it), YOU MAY WANT TO TAKE A PROFESSIONAL'S HELP TO DO THIS BUT DO YOU MUST.
That is the MOST IMPORTANT AND LONG LASTING SOLUTION TO YOUR PROBLEM.
If you do, YOU WILL CHANGE, THAT'S FOR SURE.