Reoccurring cough cold. Me. genuinly!

My son has completed 4 years yesterday . From 1 years after his birth, he has been getting cough , cold fever episode 6-7 times each year.  and getting huge medicine since then. So this is how his health is going on. his present  weight is 16 kg ,  108 cm height look like feeble . His birth weight was 3 kg. By the end of 1 year his weight was 10.2 kg.               Now present scenario Getting cough cold since 5 February . Initially 2-3 days cough was dry with fever. Doctor gave sinarist syrup and cephaxine dry syrup for 5 days and again 5 days. Now cough continues changed into wet cough . Now doctor prescribed ascoril ls  and dry syrup  after 7 days no improvement . Wet cough is as it's . Now x ray was done on 25 Feb. pneumonia .prescribed cephaxine 100 mg tablet. Levolin syrup and levolin neubeliser twice a day And solving cold syrup and one tab for allergy after 7 days , just for 1 day no cough was there . but last 2 din se again dry cough. night disturbance. help me . genuinly