I have GERD and I get alot of the same symptoms as you do but I also have a Hiatal hernia and when it's irritated i can see the bulge in my upper abs, I get alot of pains and pressure in my chest and in my back and left shoulder, along with the burping and sometimes they dont come out and that causes more pains. Best thing to do is see a GI and get on some meds. The meds will take about 3 weeks to kick in and you need to take them religiously and let yourself heal. Prevacid gave me the least side affects,nexium the most, now I am on aciphex and my muscles feel crampy but its either the GI problems or sore muscles , I'll take the sore muscles annyday.
The Proton pump inhibitors can cause joint pains to.
lots of luck