SadieM1210, there's one thing I didn't quite understand. You said the pain starts when you lay down. Isn't it there when you sit or stand? When you lay down, there is less pressure in the abdomen. I sometimes experience more bloatings when going to bed, so I often lay down before to get rid of them.
I know that kind of pain when the small intestine wants to move things on and gets blocked at the pouch, especially when there are bloatings. That also gave me a rumbling noise that could be heard when there was silence in the room. But usually you get relief as soon as you go to the toilet and poo, what seems to be a problem for you.
You mentioned CT scans. Were that live motion scans with little radiation and a contrast agent? And where are they doing that dilatation, at the pouch inlet? It must have started almost at the same time as your takedown in May.
Btw. have you tried an inverted position like half a shoulder stand to release gas? For me that's safer than lying on the side, gas always goes upward.