So, how do you know you are in depression? Does somebody told you or you feel it as your own, Lack of concentration is a generic behavior which can be as mild as due to continue stress or as broad as a real screen . You have already changed your behavior but do you really know what is your present and desired self? When you are not feeling okay within yourself than it is obvious that you will be quite. Do not worry as you are not alone in this world who feels the same about herself. If I were you than I will restrain myself from seeking my own solutions myself. You have not mentioned the duration but if you are feeling the same from more than six months than Consult nearby Psychologist / psychiatrist as it will be beneficial for you to go for medication with counseling.