D.,
Have you considered complementary medicine? Because what you are doing now isn't working long term, what do you have to lose by considering something else?
We faced the same issue that lasted until our son was 4. A friend, who is in health care, told us that antibiotics wipe out the good white blood cells as well as the bacteria causing the infection. She said she relied on homeopathy for her children's health and wellness. Once our son consulted a homeopath and she prescribed a remedy that fought the infection without killing the white cells, he got over the recurring problem. We were impressed with the results!
He was sick very, very seldom from that time on, once we made the switch to the homeopathic practitioner (also an MD). It wasn't covered by our health plan but we really saved money because he didn't get sick, we didn't get sick, and we didn't waste time taking care of a sick child or getting sick ourselves.
(If you are not familiar with homeopathy, it is mainstream medicine in Europe and used by the Royal Family in England.) See the Wikipedia entry: http://en.wikipedia.org/wiki/Homeopathy
Along the same line, I heard a short talk on ear infections by Dr. Norlin Merritt of San Rafael, CA, in which he talked about a tiny chiropractic adjustment he performs on children that allows more movement and, therefore, better health in the ear area of small children. He has found that it clears the reason for the ear infections. He and his wife, Maria, are both chiropractors who enjoy working with children. If you are open to complementary medicine, our family has had very good luck nearly eliminating disease using the two approaches. (www.merrittfamilychiropractic.com)
Blessings to you and your child!
S. Merlo