My story is very similiar to yours. My stomach was always bothering me and my PCP sent me for every test she could think of. She wanted me to have a colonoscopy as a last resort. I wasn't thrilled but when my stomach issues interupted my social life one night, I decided to bite the bullet. I had a rectal tumor as well but not as large as yours. The doctors didn't think it was cancer due to my age and medical history so they decided to remove the tumor and send for pathology. During the removal, the surgeon called the pathologist because the tumor just didn't feel right to him. Sure enough, it was cancer.
Since then, I have had 6 weeks of chemo and radation. I just got home from the hospital from having a J-pouch and loop ileostomy. I am being treated as stage III with unknown lymph node involvement. I face 8 rounds of chemo starting at the end of January and then a take down of the ileostomy in June.
Needless to say, I was shocked at my diagnosis as well. I am lucky that I live where there is an excellent cancer center. I opted to go to an office that is affiliated with the cancer center because I wanted to be a patient, not a number. I had to keep in mind the 28 radiation treatments and having to run to the hospital each day in my selection of where I got care. The treatment for colon/rectal cancer is pretty standard now with chemo/radiation and surgery. There is an oral form of chemo now that makes it a little easier to manage.
Good luck in your journey and if you have any questions, please do not hesitate to reach out.