They shouldn't discharge you if your not eating and not having movements. It is hard to eat to start with.. for around a month I had to force every mouthful.
The pain you feel probally is just gas which is savage with a pouch, and of course worse when your sore post op You probally gulped a lot of air while you weren't eating.
You need to eat (little and regular) and walk as much as possible. If you have any concerns make sure you discuss them all with your doc before your discharged...