I need help before I crack

I am an almost 31 yr old woman taking care of her 74 yr old uncle who was diagnosed with colon cancer in December 2003. He went through the chemo for that last year and seemed to be doing great. But then in December, his tests came back and showed that he had cancer in a lymph node. He had another surgery (first was in Dec 03 to remove tumor from colon) to remove the lymph node but the cancer markers in his blood continued to climb even after the surgery. Now they have him on a chemo that makes him very sick, he doesn't want to eat.

I was able to handle the first chemo treatment (last year) all right. I was strong, positive, and encouraged him to do as much as he could and I would take care of the rest. But this time, I'm falling apart. I work a job in the mornings, take classes at the university in the afternoon, and take care of him the rest of the time. His attitude is very negative, he doesn't see the use of going through all this suffering when all he wants to do is die anyway, yadda, yadda, yadda. He's been like this ever since my aunt died in 2001. They were married 50 years and he basically became a hermit after her death. They had no children of their own so my brother and sisters (and I) look out for him. If we didn't come to get him personally for holidays and family occasions, he wouldn't have come to them.

I feel like I'm at the end of my rope. I worry a lot about him because I suspect the cancer has gone elsewhere but he is refusing to have more tests done. There's not much I can do for him as far as making him better but I know I need to pull myself together... and fast.

Any advice is appreciated. Thank you.