Perhaps you are trying a bit too hard to be grateful, I mean if you're really feeling down the last thing you need to do is beat yourself up over not being 'grateful' enough.......you're feeling bad, it's hard to see the light so its understandable if you're not feeling that terribly thankful for everything. When you're in the depths of depression a few positives here and there doesn't really do much to decrease it.

You probably are grateful for the nice deeds people do its just hard to focus on all that when depression hits.

This may not make much sense but maybe its more that you aren't caring about yourself enough so it feels like no one in general does just a thought since sometimes I know i get feeling like that...then its hard not to feed it by believing no one should care and stuff like that. I am not sure of an exact solution but I have similar issues. so far I have kind of learned to think things through a bit before I go accusing others of not caring when they aren't intentionally ignoring me or anything...but I still can't always convince myself that's not going on.