hi XXXXXXX Indian (developing country) kids are supposed to get 6-8 cough cold episodes a year in first 3 years; normally. I don't know your nationality though.

your feeling of low immunity is subjective; if the child shows good weight gain on growth charts; we may say that these illnesses are not affecting the baby seriously. Please provide me detailed height, weight records.

I think you are not taking therapy from a pediatrician; often pediatricians do not give such medicine 3 times a day. you may need change of medicines depending on symptoms which if you describe exactly whether runny nose, loud cough, soft cough, noisy breathing etc. you may understand further issues in recurrent cough cold at click here

Also management of running nose is described at http://childrenspecialist.blogspot.in/2010/01/common-cold-treating-running-nose.html, its written by me.

often children with repeated cold, cough have adenoiditis and may need a xray neck lateral for adenoids to be done.

I would like to know whether each time you had been giving same or different medicines. All this including weight/height records will help me be more precise in understanding the seriousness of issue.
Looking forward from you to get these details. feel free to ask any less understood issues.
Thanks

---