Pnemonia or normal fever how to find out

My 3 year old son have pnemonia when he was 1 year old he got treatment in hospital for days and then after that for every few months he is having this digestive problems bloating or white pale motions,fever,caugh.he gets sick very often.he is a good eater but when he gets this bloating problem he stops eating one meal after one meal and then he gets sick after using syrups and antibiotics he gets normal.why is this happening how to imrpove his digestive system and his immunity.does pnemonia causes digestive problems? When ever he gets sick i get worried.now he had bloating for few days and then he stopped eating properly now from 3 days he is having fever and caugh and loose motions.his urine is yellow he gets very weakk when this happens.please do suggest what to do and how to cure my son at home.