What Causes Discomfort On Right Side Of Chest Towards Back?

sir, for some days i feel discomfort about my digestive systeme. i cannot understand what is it. i feell my hrad heavy. some times i feel sleepy. sometimes i feel some pain in the right side of my chest and going in my back. however i eat properly. I feel hungry at the relevent time. in summer i often use a mixture of milk and yougret in the morning by blending it. i m using it now a days. pls advice. my age is 36.wt.75, height 5-10. never got any serious problem of anykind in the past