Dear Susan,
I know exactly how you feel. First off, know that what are you doing is very helpful, by just being there for your mom. Secondly, the antidepressants usually take at least a week until you see any difference, and it may be possibly longer.the dosages sometimes need adjusting. Also, in order for you to stay "up", try looking into support groups for family of cancer parients. I also found this board to be a major help when my mom was going through all this. I know how terrible it is to hear..."be patient, this is normal"....but the truth is..time is your best friend....good luck! Keep us posted
Brooke