3 months old baby crying

My 3 months old baby has been crying alot more lately and has loss his appetite.. he stop to drink his milk and has difficulty catching up his breath. He is hungry i can tell but when i feed him, after 3 sec he will push the milk bottle out as if his throat is pain. Bought him to GP clinic. Dr said its just a flu.. and nothing much can be done as he is too young to be given medication.. lungs, stomach, throat all check and all is normal. This is my first born. Any mummies out there experincing the same issue? Or anything else could help him sleep better.