What were you treated with, and how long ago did you finish that up? Medications are a very common cause of nausea, and it might not clear up right away.

Are your BM comparable to how it was before pouchitis? If they are more irregular and you're also feeling stuffed after eating solid food (besides nausea), that may be a symptom of a partial blockage. If it does not get better, I would have your GI doc do an ultrasonic scan, that's not a big deal.

Protonoix and Magnesium helped me int he past. It might help you?

Could 8 liters of water be too much?  The advice I read is about 3 liters for women and about 4 for men. I realize we (with j-pouches) may need more, but I would think that twice as much may be too much. Of course, if you are following your doctor's advice, then never mind.