Hi Mandi,
There were some really bad days that I thought about giving up and then the next day I somehow pulled through it. I found myself on my knees a lot and without God's help, I didn't have the strength - but his strength is perfect. My faith got me through some very hard times.
Just because you lose an occasional battle doesn't mean you have to lose the war. I just finished reading Lance Armstrong's book and he had cancer in three places at the same time, not only lived to tell, but won the Tour de France 4 times afterward! I too have bounced back and forth between depression and self pity. I would talk to the oncologist (or whoever coordinated his meds)and see if there is something that will help - even counseling. This is a very humbling disease. Since our spouses are "mirrors" of us in many ways, this may help to explain your confusion and depression also. I will probably start cognitive therapy pretty soon myself (at my wife's urging).