Anytime anyone is on an antibiotic, they should take a probiotic to put the good back in their body. Each antibiotic that your darling little one was taking was destroying the good in his body more and more and it wasn't being replaced, so to speak. I would definitely put him on an antibiotic. Our bodies are able to fight a lot of what is dished out to us if we know how to boost our immune system and help it fight.
I too would recommend a chiropractor, but definitely get a probiotic from a local health food store. I like the Jarrow Brand...my personal favorite.
Before I stopped going to the doctor, almost 8 years ago, for illnesses (we rarely get sick anyway), I became sick with Strep...really bad. Went to the doctor, got an antibiotic and finished it, then a week or two later, got strep again, went to the doctor and got a different antibiotic, then finished it and again a week or two later, went to the doctor, again tested postive for strep....etc. You see the pattern. I got strep 4 times in a 2 month period. I didn't take the antibiotic the 4th time. Guess what I did? I went to my local health food store and explained to the naturopath what happened. She handed me something called Beta Glucan (NOW brand...it has 100mg of Beta Glucan and 160mg of Maitake Mushrooms). I took only 1 capsule a day and 2 days later, no sore throat, no strep. I went ahead and took for a few more days....about a week and gone. It didn't come back.
There are many ways to boost the immune system. I still keep Beta Glucan in the house. We've used for pneumonia, strep of course, etc. My kids use this too. I've used just probiotics for getting rid of strep too...wonderful, wonderful stuff. Good luck!