Just wanted to tell you that you're not alone. I've experienced some combination of chest pain, heartbeat, and shortness of breath in the past. I've made a couple of trips to the ER thinking it's a heart attack, get tests, etc., only to figure out it was mostly anxiety/panic attack. GERD was definitely in the mix too for me.
Lately, I've been experiencing shortness of breath. Went to a lung doctor and got tests: pulmonary function, CTs, etc., and they all looked good. A few months before, I had taken an echo stress test and a cardiac calcium scoring test. Both results looked good. I'm in the process of doing some other tests though I think I know what the results are going to be: probably OK. I guess it's a reassurance thing.
What I'm trying to say is, if you talk to your doctor and end up taking tests, and find that your lungs/heart are OK, then you have to just try to accept that. Yah, it could be GERD. If so, there's medical and surgical options for GERD (to discuss with your doctor), plus some other things like diet, lifestyle changes etc. that you can do to keep reflux in check, if indeed it's reflux. Could be anxiety too--there's meditation, breathing exercises, and other things you can do for that too. (For me, it's a little of both).
You're trying to figure out where the problem is in your body. Hey I am too. Though, try not to worry about the parts of your body like the heart, if it's been ruled out. I say this to you because I'm trying to remind myself, too! Good luck brother!