Regarding your recurrent diarrhoea
you need to consult a physicin (Internist) or a Gastro-enterologist.
Rest of your symptoms appear to be due to acid reflux
that is acid coming up the food pipe.
Normally lower end of food pipe called cardia ( surrounded by a string of muscle fibres) remains closed. It opens when food passes down and after that closes again to prevent stomach contents including acid there flowing up the food pipe (acid reflux).
In your case the cardia is abnormaly opening when it should remain closed. So the stomach contents flow up the food pipe and even up-til your throat. This acid creaets inflammation in your throat that irritates you. Hence you feel a strange feeling there and you feel like repeatedly clearing the throat.
When the acid flows up, a string of muscle at upper end of food pipe contracts trying stopping of acid going further up. This causes catching sensation in the neck. This you may feel like shortness of breath
even though in reality it is not so. But if you have really shortness of breath then it needs to be found out any cause in nose producing block or in lungs.
Acid in the food pipe causes irritation there also, giving you a strange feeling in middle of your chest and also fluid like feeling there.
What you feel as flutter could be a palpitation
due to anxiety created because of above problem.
Elevate the head end of cot (to make it to slant and not by keeping pillows below your head)
Take small frequent meals
Avoid spicy food, avoid bending forward
and proton pump
inhibitors for a couple of months are likely to relieve your problem.
has to be ruled out
For all these you can consult a physician (Internist) or Gastro-enterologist
Wish you good health