Hi,
I think you're on the right track thinking you need to think of yourself first right now. Everyone is responsible for themselves and their feelings. You're responsible for you, doing what you need to keep or get you healthy. Your friends are responsible for themselves, for figuring out their problems and dealing with their issues. It really sounds like you have enough on your plate right now, without taking on their troubles. You aren't being mean; you are doing the right thing. You need to put your problems first right now. Not wrong or selfish, just what's most healthy for all of you.
Don't get me wrong though. It's not an easy thing to do. I know I always feel guilty that I'm not doing more for others, but sometimes we do have to take care of ourselves.
Hope things get better for you, Quay