Check lungs, stomach, immune system, and other parts of the body.
i get that alot and it is because of my astma but it sounds like if you have astma then its very mild and can be controlled with an inhauler i would talk to a docter about getting one youll be surprised on how much it helps
Could be a start of fluid build-up in your lungs. I would certainly get this checked, you need to have a chest x-ray to rule out any fluid in your lungs.