Doctor I Have History Of Dust Infection In Starting.Now That

Doctor I have history of dust infection in starting.Now that is same situation with my baby.his health is detrioting ftom last sept.He(2.7 year of age) suffered from pneumonia and then off and on fever cold and cough.He is firstly pricky eater.We have to forecefully fed him everyyime.Two day back again fever came and gone to doc .Now chest is clear but cough.He is there due to throat infection.Due to coughing not able to eat properly.
This time doc suggested these medicine and d3level test.D3 level test details I will share in evening.

Syp Ascorl 3.5 three time a day
Syp montrel 5ml 15 days at 4 to 6 pm one time a day
Zinc syurp 5ml 14 days one time a day
Levolin 5 days 2 time

Above presriptipn is started on sat
And we gone today i.e Tuesday after seeing D3 report she suggested tab d3 tablet for 20 week.
Budate 2 time a day for three day.

I wrote so big so that doctor can understand my tense mind.We are really confuse as baby immunity is weak which doctor say but how to improve.Is these medicine are worth to give.As he dnt feel to eat and everytime khicdi he dnt like.And coughing like hell if we dnt nebualize.Now days we are giving so many medicine.Feeling confused.

PLease help doctors .Needed it badly...This is question of confused and crying mother.Not able to see my baby in such situation.