Sadly, however much you achieve or how ever much you are good at something etc. If you have a poor self-image it will never be good enough. It sounds like you suffer from low self-esteem and this is making you depressed. The depression is causing you to feel the way you do about your career and your life. Once your state of mind has improved you will see things and your opportunities in a different light. Maybe take a visit to your Dr to see if he can give you something to lift your mood.