For the longest time, my panic attacks manifested themselves purely as "gastric upset". That's a broad term, so to be more precise I'll say I'm intimately familiar with the burping. My doctors tell me panic can affect any body system. IBS is also known to have a connection to anxiety/panic disorders. I think I have a irregularly irritable bowel as a result of anxiety. That's to say I don't have IBS symptoms every day or anywhere close to that, but I do get them sometimes. And I hate to get too personal here but it used to be that every time I'd go to the can and have loose stools, a panic attack would follow. Every single time. I never really figured out the connection there, but there must of been one and it must have something to do with anxiety. For me, anyway.
GERD can also cause burping and stuff. And GERD is worsened by anxiety. Go figure. So you may try some Tums or Maalox (with simethicone) to see if that helps.
In short: Anxiety makes everything worse. Get the anxiety under control, and chances are everything else gets better to at least some degree!
My Brain: My friend, My enemy: A blog to chronicle my attempt to recover from anxiety/panic disorderanxietypanicdisorder.blogspot.com/