@susan38 A couple of thoughts: In Britain, the oncologists routinely offer colostomies prior to treatment so that the feces are routed through the bag rather than through the rectum and anus. I would imagine that this would reduce the pain in that area and would allow for more regular emptying of the colostomy bag rather than dashing to the loo when diarrhea hits.
Have you discussed your home situation with your oncology team? Might there be a nursing home where you could stay while being treated?
If you need to stay home, can you clear a path from the bed to the loo? Do you have friends who can help you get to your treatments, pick up groceries and meds? Get their commitment ahead of time, and if possible get someone to be "point man or woman", organizing things like ride schedules so you don't have to do that.
A nurse at the cancer center should be able to give you advice on how to stay clean, what items to buy in advance like a sitz bath, what kind of wipes, creams and ointments that will be gentle on your skin, etc.
Wishing you a gentle journey through this. Don't be afraid to ask for help. You'd be surprised who will step up.