I think I am in the same situation.

I have finished radiation (feb 7th) and had a sigmoid only 2 weeks later as I developed an anal fissure from constipation, point being, my tumor was gone visually only an ulcer left and biopsy came back clear.

I start CAPox regimen on Thursday, as I have lymph node involvement but I am very confident in beating this cancer and putting off the surgery. I have come to terms with a possible ostomy though but I sounded just like your post right after diagnosis. I was most concerned with my marriage and our sexual relationship.. but my husband said we can make it through anything and I have heard they have bags now that filter any unexpected gas etc.
and they have bag covers…..

After going through constipation with an anal fissure, I was honestly wondering if I could make it through all treatment! I was in the ER screaming in pain while trying to have a BM. It was the most painful moments of my entire life thus far so let me tell you that a bag sounded like heaven!

Good luck and I will pray that you are able to feel more comfortable IF and only IF that becomes your only treatment option but I bet it’s not after rad and chemo