My husband struggled at times too- men like to be able to fix things and they can't fix this - a cancer diagnosis is scary, and the treatments can be difficult. It is hard to watch someone you care about go through this.
The ladies above have made some good suggestions.
The things my husband did for me that made me feel better included:-
Coming to appointments with me
Helping me to do chores I could not manage
Asking me what he could do to help
Discussing things with me
Giving me back rubs when I was sore from spending too much time in bed
Helping me dress
Telling me he was happy to help
I am not sure of your situation but I know I hated to ask for help as it highlighted what I could not do, equally I got frustrated because I could not do things. I know I could be difficult.
Sometimes it is just enough to be there to rub cream in or pass a cool flannel or hold a hand. Sometimes that's all it takes is to be there willing to help or listen.
I hope you can find someone to talk to to help you work though everything you are feeling - this disease affects more than just the person diagnosed and treatment can be like a marathon - hang in there you will get to the finish line
Sending hugs
Chris