Okay, Ive been through this and understand you fully. You dont have asthma. You are just super aware of your breathing at the moment due to anxiety and focusing on it. For myself, when I was in the same situation I also thought asthma or low lung capacity or something. What it is for myself is 2 things. 1. Food and or outside allergies can make breathing a little constricted but absolutely nothing to worry about. 2. High histamine foods absolutey made my breathing somewhat shallower. Google high histamine foods and low histamine foods. Once I went to eating low histamine foods it dramatically improved my breathing and anxiety (actually my anxiety went away 100% a couple years ago). Anxiety and the breathing issue in my personal opinion are food allergy/external allergy/high histamine food related. Again, this is my opinion because it worked completely for me.