It could possibly be from stress. I'm kind of taking a shot in the dark, but it just sounds kind of like what happened to me. I didn't feel "normal".. I didn't think I really felt stressed, just agitated and restless i guess. That caused more stomach acid to be produced and it caused pressure all over my abdomen and chest. Its strange because a lot of times the pain doesn't come from the stomach area or your throat, but pains in your shoulders and arm and lower stomach and stuff. It would be good to get a checkup and your heart checked just in case, but don't worry too much about it as that will only exacerbate the problem.
The difficulty swallowing also makes me think of stress-related issues. For some reason, thats one of the symptoms of high levels of anxiety. Again, I'm not saying if thats the reason or not since you didn't mention anything about stress or anxiety, its just something to consider. What I took was Omeprazole (pretty sure its generic for Prilosec) and after a week or two, I was feeling much better. And if you do think that anxiety could be the cause of this, mention that as well to your doctor. Try taking time out to just close your eyes, take a few deep breaths and try to calm yourself. Hope I could help.