I went through a period of a couple years with really bad anxiety and depression, although I didn't realize it at the time. Heart palpitations, chest pain, stomach pain, and fatigue were the physical symptoms. I had all kinds of tests run thinking that I had a physical problem but it turns out that the depression manifested itself as a physical condition.
I've had a few panic attacks over the years as well. Feels like you're having a heart attack. I could feel it coming on as my heart would start racing for no reason and the more I focused on the what was happening the worse it got. The only way I could get through it was to distract my mind. I would turn music or television on and just take deep breaths to slow my pulse down.
I assume that you're on medication, but if not I'd see a doctor. It took them awhile to figure out something that worked for me but eventually I got back to feeling normal again. If you want to talk it out with someone let me know.