I would agree with what the other poster said about quitting cigarettes. I have smoked them off and mostly on for many years along with herb. When I have quit I was struck by the negative impact they have on breathing. Weed seems more irritating if smoking cigs. Plus your doc says you have reduced capacity- smoking can only hurt this.

The fact that your symptoms go away when drinking is diagnostic I think. Hints that anxiety is the root cause- a primary symptom of anxiety is perceived shortness of breath in the absence of lung disease. THC can trigger anxiety and alcohol- a central nervous system depressant can relieve it.