Feels like pocket of air in mid left back? feels weird to lift arm. i do have some gas, but scared this might be lungs. sharp pains occasionally?

Get seen in person for a history & physical if it continues.

I agree that you should be examined and advised by a physician. I assume there has been no injury or recent strain. I doubt lung etiology and, at this time, I think the symptoms are emanating from the rib cage. A pinched intercostal nerve or muscle that runs between 2 ribs can cause sharp,fleeting rib cage pains often precipitated by a deep breath or other rib cage movements.