“How does a doctor observe shortness of breath?”

In a doctor's notes from a recent follow-up visit for an orthopedic problem, I was surprised to learn under the review of systems that I was positive for shortness of breath. I was not aware of having any breathing difficulty nor has breathing ever been discussed during this or previous visits. My oxygen level at this visit was 98%. At one point during our conversation I began crying/sobbing under my face mask - could that have been mistaken as shortness of breath? Is there something else she could have observed to lead her to determine I was short of breath?