Hello dear, thanks for your question on HCM. 
I can understand your situation and problem. 
In my opinion you are having uncontrolled GERD ( 
gastroesophageal reflux disease ) mostly. 
Since your extensive pulmonary work up is normal, no need to worry much for pulmonary causes. 
Uncontrolled 
acid reflux can cause 
chronic cough and breathlessness due to micro aspirations. 
And following lifestyle modifications along with drugs are needed for complete control of GERD. 
So avoid stress and 
anxiety. 
Avoid hot and spicy food. 
Avoid large meals, instead take frequent small meals. 
Go for walk after meals. 
Keep 2 - 3 pillows under head in bed to prevent reflux. 
Avoid alcohol and 
smoking, if you have these habits. 
Loose weight if you are obese. 
Don't worry, you will be alright.