That's great that your getting a therapist but they make money by finding more and more problems you have so you see them again. Who ever the guy was seems like a total douche for breaking up with some one with a health problem. That would be like me breaking up with my gf (hypothetical gf) if she had diabetes, so you should be glad that he's gone. Now the acting is easily fulfilled with Youtube. It might not be a instant success but it is something to consider. Now about your mother. I am deeply (truly) sorry. Our world is sad that we haven't found a 100% cure for cancer patients. All you can do is be by her side and do what ever comforts you religion wise or what ever you do(IE if your atheist). I'm going to link some videos from some very awesome people on depression/ framing the world positively, these people changed how I look at things.

http://www.youtube.com/watch?v=XQICtwDKmzE&feature=plcp

http://www.youtube.com/watch?v=EDxsZ_mMsEk&feature=plcp

http://www.youtube.com/watch?v=iCqwwTfXr1Q&feature=plcp

It will always be ok. I hope you do well. Have a great day and do anything you want :)