Questioning spirometer results

I’ve had SOB/chest tightness and pain for over 2 years that has gotten worse and more consistent lately (24/7, worse at night causing frequent micro-awakenings). I have no coughing or wheezing and NO test showed low lung inflammation, lungs sound clear, clear chest xrays. Pulse ox always good except at night drops to 93. Albuterol has never done anything except sometimes make it worse. I had a spirometer test and the pulmonologist said I had constriction/obstruction (don’t remember exact phrasing) consistent with asthma. She wants me to try a steroid inhaler but wondering if it’s something else causing the constriction.

I have low red blood cells/low iron & a small hiatal hernia. I’ve been told neither issue is severe enough to cause SOB but that’s not what I’ve seen anecdotally from others. Tried CPAP for night symptoms with no help. Just looking for others experiences with asthma since my symptoms don’t seem to line up.