Hey there, theelt!
You remind me a lot of myself. I'm a college student with a pretty bad case of cardiophobia. I had my first panic attack in June 2010 and raced to the hospital convinced I was having a heart attack. I had the works - shortness of breath, intense chest pain, and just a few blocks away from the hospital I lost all feeling in my hands and feet. At the hospital, they found nothing. They told me it was anxiety. It seemed incredibly unfair that my brain could do that to me. It still does.
It's been almost four years and anxiety is still my biggest challenge in life. Some people with anxiety say that their physical symptoms, including those scary chest-related ones, start after they're already anxious. Unfortunately, that's not me! I can be feeling pretty decently, when all of a sudden the chest pain begins. From there begins a chain reaction that gets harder to stop the longer it goes on. If you can successfully ignore and toss aside that first stab of pain, your odds of continuing on with your life normally are high. But if you pay attention to that pain, your anxiety will enhance it and magnify it, and new pains will happen.
Disregarding the pain is very, very hard. I can only rarely manage it. But that's the key.
Your bloating and burping and reflux is likely the culprit of your chest pain, perhaps in combination with the tightening up of your chest muscles. Anxiety, and the stomach/chest sensations it can cause, are so cruel in how they mimic some of the scariest health emergencies humans can experience.
That sudden chill when the room temperature seemed to drop? A classic symptom of fear. I bet you that chill was accompanied by some sort of mental "oh my god" thought. The "oh my gods" are the worst kind of thoughts to have when you have anxiety. And I'm not talking "oh my god" like "oh my god, i forgot to buy cat food". It's the sort of "oh my god" that means you are bewildered and terrified of that feeling you just had. I have a lot of trouble with those too. When a terrible, terrible, downright awful feeling has just affected you then it seems natural to be frightened of it. But, unfortunately, anxiety does not play fair. Even if it seems natural to react in that way, having that sort of reaction just makes things worse. It is hard to stop. But it's the reason why the fear cascades.
The odds of you having a heart problem at your age is incredibly tiny. I'm 26, a whole decade older, and my own chances are still very small.
Have you ever had an EKG done? It's a test that checks out your heart. I know you're uninsured, but an EKG at an urgent care center is usually cheap compared to an E.R. visit (my E.R. visits cost thousands of dollars, but an EKG at an urgent care clinic might be as cheap as $75 and very rarely more than $175). I very, very, very strongly doubt that your heart is the problem. However, an EKG might give you a bit of peace of mind. My last EKG's results, given to me two months ago, are folded up neatly inside my wallet and I look at it whenever I feel bad.
After you come to accept that it's not your heart, things will get easier, but it's only the beginning. Anxiety lingers even after reassuring test results, so I strongly recommend seeing a psychologist if you haven't already. I know it's hard when you're uninsured - I am too. But it's not impossible. :) My first ever appointment with a mental health professional is in just three days and I'm excited.
Best of luck!