The last 4 months I noticed I would breathe very heavy when working(building patio) as time went on my endurance decreased daily. Now showering, putting on shoes or just walking through house has me SOB. I have been tested and and all my blood, heart, lungs, organs check out clear and in good shape. It is almost more a muscle seizure then needing air. My pulse doesn't rise and O2 levels are good during episodes. These SOB episodes have had my gasping and chocking for breath. I become very dizzy and light headed, diaphragm, throat and chest muscles seem to contract erratically. Has anyone had a similar experience?