Welcome to the board, and sorry to hear about your difficulties!
Firstly, a matter of definition, but it might help alleviate some of your anxiety. Technically speaking, there is no such thing as temporary GERD. There is "normal" reflux that anyone can experience because of overeating, illness, spicy foods or other trigger foods, etc. GERD is a dysfunctional condition where reflux happens multiple times per day, as a result of a malfunctioning lower esophageal sphincter. The only way to get diagnosed with GERD is through tests that a GI doctor can perform.
The purpose of the Prilosec is actually twofold. First, is to hopefully alleviate your symptoms. But secondly, if your symptoms DID improve, this is a simple method your doctor can use to help him begin to diagnose what's happening to you.
It sounds like you're on the right track with the appointments you've set up. There is a wealth of information you can gather here from this messageboard, and you can start with the "stickies" at the top of the main page.