Sometimes we just shut down. I've been where you are (mentally that is) because I was overwhelmed and stuff, and I just shut off. I couldn't care anymore. So what I did was I forced myself to go through the motions of caring, even though my heart was not in it, so that when my mind snapped out of it -- and it will -- my body still knew how to do all of the things I would want to do. Plus I feel like I regretted less from doing that.

That being said, I couldn't do it all the time, so maybe plan to see friends 1ce a week, or take your sister out and make her feel like you at least care about her (that goes a long way). I know it's difficult, but just going through the motions will help in the long run. Your power will come back on when it feels it can deal with the amount of pain around you.

Also, Thunder Bow is right, a T would help.