Have you ever considered going on call-in show and discussing your pretty profound family problems with stef?, I bet you could get put to the front of the queue if you explained your situation to Mike, and if you feel to anxious to talk live on the podcast I've heard Stef offering to people the option to talk in private.
Talking with a therapist is another important action to consider, I'm not sure how the school system works in Germany, but in my high school in Canada there's always a few therapists available to talk to (although their quality as therapists might be questionable since they're working in a public school) . But other than that I don't know what advice I should give you, I just feel incredibly sorry for the situation you're in with your mother and your health problems. If there is anything you want to ask me I'll be happy to help.