Is he in daycare?
I can say that my little guy is three and we went from being sick all winter long, to a couple times a month and now we are down to once a month.
I guess it depends on what kind of sick you are talking about?
I insisted that my son have his tonsils and adenoids checked by an ENT and I'm glad I did because it has helped some. If your little guy snores, maybe have him checked by an ENT.
In the meantime. Antibiotics can sometimes make things worse. My son has been on them so many times. It's hard as a parent to not worry and think they need medication especially because we can't even give OTC meds to help their symptoms. Probiotics and a very good multivitamin taken religiously will help. Try to build up the good bacteria in his body again as this is destroyed by the antibiotics and will make catching a cold, runny nose or any congestion easy to catch. Lots of yogurts and little sugar will help too. It will take time, but hang in there
Hang in there!