As a therapist I work with depression, stress,etc all the time. Do I think stress can affect one's physical health? Yes. Do I think you caused your mom's cancer? NO.
There are people that deal with unbelievable amounts of stress for years and remain healthy. There are people that deal with minimal stress and get sick. And everything in between.

I think cancer does not discriminate and very often it is so hard to make sense of . It affects people of all ages, male, female, all races, ethnic groups,etc. It affects people who have stress and happy go lucky people.

Self loathing is miserable and I feel for you. I very much hope that you are getting help to deal with those feelings. That has to be such a rough way to live.

As a parent,I would never, ever want my kids to feel responsible for my health. I'm guessing your mom feels the same way