Welcome to HCM
We understand your concerns
I went through your description. Your description itself has lot of answers and it clearly shows how confused you are.
Acidity or acid reflux
problem happens due to indigestion
due to junk food or excess of digestive liquids inside stomach. Acidity creates gas and gas pressurizes diaphragm thereby creating chest tightness
or suppression and pain, followed by belching
Every tests came negative and you are sure that he is in a very good shape. Rigorous exercising regularly can do wonders. Including garlic and ginger regularly in your diet, using cumin seed decoction can also help better than antacids.
More importantly, ask your husband, not to worry too much. Anxiety
also causes multitude of these problems. He should be cheerful always.
Hope this answers your query. Available for further clarifications.