Weakness is all a matter of perception. You need to think about the weakness in not taking action to make yourself feel better about your life... because the easy route is to pretend everything is ok, but you need courage to face yourself and change the way you feel.

You may need to start looking at your life from the outside in to realize your actual situation.

You are feeling alone due to your lack of social interaction? If this is the case you should look into how you can replace your old activities with new ones to fill the void you are feeling. Finding a sport to play would be great so you can get a sense of competition back into your life, get your adrenalin going and also get the social interaction you desire... but there are a number of other things you may want to look at doing.

In relation to the flaws you feel you have, what are they? If you can list the things you feel are your flaws then you can look at two things... 1 - is this thing a flaw or just an insecurity you have?... 2 - What would you need to do to feel positive in this area of your life.

To be more confident in yourself you need to change the way you feel about these areas of your life by doing activities that will improve your ability in life. Some things take longer than others but at least you can start taking it step by step if you know what you want to improve.