Hello doc i have a son of 3 months old,

After each feed I am burping him well then also he splits the milk in Little bit vomit form or else the milk which I feed him comes from his mouth.  after bath  he splits milk and after tummy time he splits the milk,he mostly Archies back some times.during hiccups he splits milk and while craddle him on the hands he splits and after 1 hour he ask milk and he is passing urine more than 12 times a day .he is completely on breast feeding.i cutted down the diary from my food caffeine also reduce.he is active and takes milks .but he is also facing dry cough during feeding and some disturbance in sleep.if he takes dreamy feeds that time no splits majority but if he is awake definitely he splits... what is the solution he is born with 2.5 kgs and now he is 5 kgs .but from 2 month to 3 month he gained only 500 grams .i feed him very often in the day time..what is solution and medicine .i am also using vomting syrup but no use.