Hey ronin, what emotions are fuelling your urge to cut? There are several different strategies to adress these emotions and/or fulfill the needs implicated in them in a way other than cutting.
EDIT: Sorry, I somehow skipped the two short paragraphs in the end of your post.
You say heavy loneliness that's painful to bear makes you want to cut to take your mind off of them. I guess there's home sickness involved, too, and sadness about the way your brother's behaviour has changed. Hm...
Is there really no way you could seek company? Interact with some animals, maybe at a shelter? Have you ever talked about his behaviour to your brother? Maybe he doesn't know that he's changed so much.
It's not much, but you need to stay pro-active if you want to stop slipping. Do something to improve your situation; even very little things can have a considerable effect.