a child of his age can get 6-9 viral infections per year on the average. if each one lasts a week or two it can seem that he is sick all of the time. the more exposure to other children the more likely he will share those easily transmitted germs. it is normal to be concerned about his immune system but as a child his immune system is inherently immature -- children do get sick more than adults and older children. they tend to be better after age 6. as you know i have no way of specifically determining why he seems to get sick so many times so you will need to bring this up to his medical provider.
my 3 year old gets colds once or twice monthly since he was 6 months. he eats right and is active. what's your advice?