Nausea is common with GERD. I wouldn't pay for the MRI just yet. They're awfully expensive!
Are you on a good prescription strength PPI? They do help with nausea. Not everyone gets relief with all of them though. I only used Aciphex and Nexium. The OTC ones are only half strength.
You mentioned you have a "do not eat" list. Do you have any suspicion your foods are triggering your reflux or nausea? Any other symptoms? Rapid heartbeat or feeling of a gas bubble in the stomach? You might check out some of the threads on food allergies or food intolerances in the search box at the top of the page. Also, try keeping a food journal (see other threads).
I don't know much about those two meds. You might look up side effects on drugs.com or other reliable websites. Nausea is listed for both.