I have been having some trouble breathing since quite some time. Most of the times, it is nothing but sometimes I have to wait and breath air deeply through my mouth 2-3 times to feel normal/full again. From time to time, I also feel a slight sensation of pain in my chest. Very slight, but it does happen, on the left upper side. Side note: I have had historically high hemoglobin, (in the ranges of 17-18.4, I got checked by a hematologist who did blood tests and it came back all clear). I am a 20 year old male with normal weight and height.