I think it's not that you don't care...it's that you care so much that you don't. You make yourself numb to that feeling..This is the way it is with me anyway, and I'm only guessing this is probably the same for you. I know that I don't have any empathy or feel so disconnected and like a stranger to people at times because I feel like I myself am like an alien. I feel like I'm not good enough, like they are living on a different world to me, socialising for fun whereas socialising for me, is incredibly hard and painful. I'm learning not to compare myself with other people though and just to do the things in life that I enjoy. I think it's so true when they say people will only like you if you like yourself - when you treat yourself with as much care as you would give another person, then can you truly socialise and make friends- just by not caring what others' think and putting yourself first. I think low self esteem is definitely the reason that you feel this way.