Hi Alex, it definitely is from the surgery! It takes a long time to heal inside.
I was gobsmacked to wake up with a colostomy bag! I didn't think it would happen after avoiding it the 1st cancer.
They gave me a radical hysterectomy and operated on my bladder but my colon died on the table and I became a permanent ostomate. After my surgery I looked 6 months pregnant and was incontinent for about the 1st 6 weeks. By 12 weeks after surgery I looked about 4 months pregnant and had control of my bladder. At 20 weeks I had a small round belly that was bigger on the ostomy side by about 1 and 1/2 inches. That means using 1 and 1/2 wax rings to level out my barrier and bag to prevent leakage.
At 2 years of being an ostomate, my tummy is the same, mostly flat with a small mound around the ostomy. I still use 1 and a 1/2 wax rings to keep everything level.
Nobody has ever noticed I have a colostomy bag and unless Moana gets noisy or busy ;). I just have a little round belly lol
Good luck!