Im sorry to hear about your symptoms. Now from what you are describing it sounds like that you may have developed a couple of conditions. The first one which comes to mind is that you could have developed arrhythmias, which is a condition in which the heart beats regularly and quicker than usual. This can cause palpitations, fluttering of the chest, shortness of bfreath, coughing, sweating, chest pain among many other symptoms. This would need t be evaluated with the help of a simple EKG, a echocardiogram as well as a 24 hour holter monitor test. Sometimes arrhythmias can be missed on a simple EKG and thats why the 24 hour test has to be done.
Another cause can be a problem with the stomach which can cause acid reflux which can result in these feelings as well as the cough. This can worsen when you lie down and would also cause a bitter taste in the mouth as well as burning in the chest. The diagnosis can be made clinically however sometimes an endoscopy is required. I would suggest that you start using OTC prilosec and see if that helps.
Lastly this can be a problem with the lungs themselves sometime a little fluid in the lungs due to an infection etc can cause these sort of symptoms, a simple xray or if needed a CT scan of chest would rule this out as a cause bit i think you should have your doctor look into the above conditions first as possible causes here.
Do you have any more questions?
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