I honestly feel it's the result of your Bulimia. After you have forced yourself to vomit for so long, it becomes a normal reflex to the body to vomit after eating without any help from you. It will take some time for your body to "learn" not to do this. It would help to add yogurt enriched with probiotics which is a natural occurring bacteria found in our intestine that aids in digestion. I'm sure your system is depleted of this after all you've been thru. Try antacids for gas and stomach acid. Instead of 3 big meals, eat every few hours in small amounts, this will be easier on you stomach. Your body has been thru a lot in 10 years and is going thru an adjustment period, with time everything should improve. If you haven't had an Endocscopy I would request one be done by your Gastroenterologist to view your stomach and make sure everything is okay. What did they say caused your bowel prolapse? Congratulations on getting better, I know it's very difficult and it sounds like you're headed in the right direction. If you're not happy with your current gastro doc, find another, there are good and bad ones. I do wish you all the best and take care.
maybe try very mild, bland food. That may help w/ the belching, acid reflux, nausea and may actually stay down.
If that doesn't help you maybe you should get a nutritionist.
It does sound like gastroparesis. You should ask your doctor for a gastric emptying scan. Good luck.