Is it worth changing milk if the baby has a cough?

Hello. Please give me a hint. The doctor changed the milk for the baby after the nose flew a runny nose (water) to Bebilon pepti milk. After this milk began to terribly downpours even vomiting settles very rarely and has a suffocating cough I was with him at the doctor got 12 injections because the doctor said that he has like inflammation of the upper respiratory tract injections he ran out I was again at the doctor doctor said that the son is nothing and you do not have to do anything about it and still has a suffocating cough even until he breathes can not sleep because the cough tires him at night I wake up a few times where before I got up once or twice just to eat I asked the doctor to change his milk but he said that it is not from milk. It has been going on for a month and the son is 4 months old. Change his milk to the previous one that he had, i.e. Bebiko or continue to keep him at bebilon and as the doctor said to inchalowac him. Please help. Is it possible to report such a toddler to another doctor and what specialization because I do not know