What Causes Wheezing In A Child Who Is On Formula Milk?

Hi, My 5 month old baby who is taking formula milk since birth has been advised to use a Nebulizer with Duolin Rapsules, alongwith other drops like T-Minic and Nasal Saline Water. Since last few days he takes heavy breath, makes whizzing and whistling sound and sneezes for 5-10 times a day. He also was able to drink the milk properly since last 2 nights. My Doctor said that the reason for this condition is because of formula milk, my wife is really depressed because of this and we both wanted to understand if it is true, or this condition can even happen to infants who are on mother s milk. Also, what all things do we need to take care incase of a baby who is in formula milk since birth?