Breathing issue. Eliminate this issue.

BREATHING ISSUE : - There is shallow/incomplete breathing when I am in a static position, when I am sitting or standing. I sit most hours during a day since my job is a desk job. - Due to this, I have to take very long breathes after small intervals of time. - When I am lying down, or I am in a sleeping position, basically when my body is in a HORIZONTAL position, my breathing is perfect. BUT when my body is in a LATERAL position, like sitting or standing, then there is this issue with my breathing. Its shallow or half breathing. - When I am walking, running, gymming, or my body is in a moving position, then I can breathe properly. - It also seems like there is a lot of mucus/phlegm/cough stuck on my chest or in my respiratory system. Whenever I clean my nose and throat every morning, I can feel that. I think this phlegm needs to be eliminated from my body. Please assist me to eliminate this issue.