Bloating & out of breath. Should i do?

When I climbing stairs, cycling or any household work even mild activity.. my abdomen becomes tight and bloated with breathing out ,rapid mouth breathing ..i tested ecg,tmt,hrct chest,all blood test,upper gi endoscopy,USG but nothing coming out from it ..more often I need to take manual deep breaths , sometimes I feel weak legs , burping etc ..after opening eyes in morning I feel my breathing very fast and I had to take deep breath manualy but  after  sometimes waking up it's gone..?  Sometimes during walking my chest very tight then I am to take manual mouth breath....What would be the possible reason of my breathlessness/ manual deep breathing with bloating, burping? I visited many doctors md, cardiologist,ent ,one pulmonologist but they found nothing...So what should I do ?