my son is 2.5years old and has had a cough for over a year now, had 3 chest xrays all shown bronchiolitis, most recent report said 'there are persistent mildly increased perihilar bronchovascular markings' my question is why is my son not getting better? why is going on for so long? is there anything I can do to fix this. Also my son was born at 36 weeks and only weighing 4lb14oz. really don't know where to go from here....

Thank you