ill tell you what usually helps me..
case may be a lil diff but any advise might help
..
when you go into your room... turn on some music... that you like .. better if its not talking about suicide or the likes.. (just because it will keep you thinking about that)
and (just to be sure .. r u a male or female?)
i read in another post that you r 15 rite?

but ok..
i have been through something similar.. and well it helps to write things down.. after that you can tear the paper up or whatever..
if you dont want to do a journal like thing then make it into a poem or a song or something..

as far as the shopping goes.. i can still only suggest things to try... you might ask if you can -if ur interested in video games- ask to go to the electronics and have them run by to get you when they r done..
or maybe bring something to listen to while you walk with them..
if music doesnt help then i will try to help think of another way.. but music is a big influence for me...

Hope this helps..
best wishes..
and i know you have prolly heard this a dozen times but
things tend to get better even when they r at their worst
:-D