Heartburn questions.... GERD?

I have been suffering from daily heartburn for over a year and a half.  About six months ago I had a barrium swallow.  The results basically said no indication of reflux.  I was given both Nexium and Zantac to try... Nexium gave me bad hunger pains all the time... Zantac didn't really seem to work.  I have been getting by with antacids and pepcid AC (not sure why this works), and am seeing the Dr. again next week.  In the mean time, a few questions for you all.  

1. Daily heartburn is an indication of reflux (NERD or GERD) right.  Why would the barrium swallow not indicate reflux?  
2. Are there other causes of heartburn that are not NERD/GERD?
3.  My heartburn is always associated with a burping feeling.  That is, I feel like I have to burp, and up comes acid (and gas of course).  Is this a normal symptom.
4.  Should I have a different test done.
5.  Should I see a specialist... or so, what kind?

Thanks in advace.