Sorry to hear of the rough times. I had some PEG troubles as well. Christine gave some very thorough information.
Remember that pain meds can also cause nausea. You may not be on any yet but if you do, the Duragesic Patch made me really nausea and vomited a few times. This happened while taking reglan, compazine and zofran. For me I had to get rid of the Duragesic and go w/ oxycontin and lortab by PO or peg.