I don't know about the ECG interpretation. It would also be helpful if you give more about your physical condition (thin, obese, sports, diet, other pains, etc.) Being from the armed forces, can we assume you're quite fit?
I would advise that the first thing you clear up is your nutrition (if you still have not done this). Get into a good diet plan that supplies more than enough protein and does not raise blood sugar/insulin levels. Consider your magnesium intake, too, as well as other minerals. Lots to consider about nutrition, but start with what you're already eating.
Monitor your diet and activities so that the next time you feel some pain, you can backtrack and see what you did and ate. Simply doing this can pinpoint a lot of causes of problems. Monitor the opposite condition, too: when you don't feel pain, what was it you were doing and eating?
As for your cardio program, I hope you don't still believe the aerobic myth. (What do they teach in the armed forces these days?) Get into an interval training program like the Tabata protocol
or its variations, and you can have a most effective cardio and fat loss program all in one, and in under 5 minutes. Be sure to get into your program gradually, and as in the last paragraph, monitor your body's responses.
Also, start a breathing program. Full breaths at least 100 times a day. Your thorax/lungs may not be expanding fully, and this may be a cause of poor heart function/pain. You may also go into breathing exercises like 1:2:2 or 1:4:2 inhale:hold:exhale ratios.
To your progress,