Sorry you're having rough time, but you have managed to give me a name to same thing that happens to me after every surgery I have ever had. For 5 days after surgery my stomach doesn't drain and so I always have an NG tube which they have to drain all the time. Even when they then say I can drink, it just sits in stomach and is incredibly painful and stretches stomach until I am sick. For some reason that action then seems to get bowel moving, never knew why until I read your post, didn't realise it was an actual condition, just thought it was my stupid body!
As to how to improve things now. I had bad stomach acid after a reaction to anti inflammatories few years ago. They put me on Omeprazole and if|I remember it did take good 6-7 days for them to start to really make a difference. Hold on in there, it is still early days but would be worth having a chat to your GP/GI to say if there is no improvement in next few days. Also try to keep to non acidic foods, no citrus fruits or cordials, spicy food etc. May be boring but bland food and small amounts at a time for next few days to see if improvement and keep upper body upright and straight for couple of hours after eating.
Crohn's dx 1989, loop ileo 1992, end ileo 1992. Arthritis developed 1990 Stoma abcess 1995. Azathioprine started 1995. Panprocolorectomy 1999. Stillbirth 2000, antiphospholipid syndrome dx 2000. Flare up 2004, stoma abcess and strictoplasty 2004. Low blood pressure dx with impaired kidney function 2006, fludrocortisone pres. flare up 2010, steroids, Humira, codeine.