cloudy chest xray

my son is 18 mth old he has had 4 chest infection in 12 mth he has been given a salbutamol inhalor the last infection he had made his asthma worse and we took him to a&e he was strugling to breath. while he was there they did a chest xray which showed up cloudy areas on bottom of both lungs, they said it was probaly an infection and gave him anti biotics. i have an app to go back in 6 -8 weeks but i cant stop thinking about this xray he has finished the ani biotics and is fit and well and the dr says his chest sounds clear. please help to put my mind at rest, if it was any thing serious would he have other symptoms ?