Your problems seem to be related to a low self esteem. It is not clear whether you have a psychiatric disorder like social phobia or depression. To improve your self esteem you will have to identify its sources. These are usually lack of competence - perceived or real - in domains important to you. For example, professional, social, emotional etc. Focussing on ones failures and weaknesses and ignoring the achievements dents your confidence like nothing else. Identify your areas of competence and value them. Improve the skills which you lack e.g. communication skills, asserting yourself, problem solving and any real skills which help you in achieving your professional goals. Learn to relax by yoga, meditation or any other method you know. I advise you to consult a psychologist who will help you systematically by behaviour or psychotherapy.