Is it normal for a 40-month-old baby to catch a cold frequently?

Hello doctor,

My son is 40 months old and weighs 44.09 lbs. He joined play school around ten months back and has been prone to cold every month. He also gets cold if he travels to a new place by car. During his cold, he is active, eats well, and bowel motion is also normal. Every month I use any one of these as per the doctor's prescription. For running nose, I use Cetrizine and Levocetirizine. For mucus in the throat, I use Ascoril LS, Maxtra, or Mucolite. I use the antibiotic Augmentin DDS syrup.

This time too, for the past 7 to 8 days, he has mucus in the throat, and I gave Ascoril and Cetrizine (the first three days); after that, Sinarest and Augmentin DDS syrup and giving steam twice a day. The improvement is good, but still, during brushing, he is coughing out some mucus. I am planning to opt for an anti-flu vaccine, but due to this cold, it has been postponed. Please guide me in improving his immunity to cold and any change in medication if required.

Thank you.