You say that you are dealing with
stress in your life, which indicates to me that it may be anxiety/panic
disorder (but please do not quote me on that as obviously I am not a doctor), but I do have personal experience of what you are currently going through. Have you had the relevant tests done as in a chest exray, ecg, ekg, blood tests and so on? and if so, what have all of the results read, and why is your doctor prescribing you medication? did he diagnose you with anxiety?