My daughter got frequent ear infections just before her brother was born (what timing! 9 mos pregnant and dealing with a sick 2 year old). I believe there were 3 or 4 back to back covering a month or two. Finally the doc gave her a much stronger antibiotic (it was called augementin) and they finally cleared up. Apparently there was some bacteria that was resistant to the regular amoxicillin and it just made the infections come back, opening the door for the regular bacteria and getting stronger each time. Once she was done with the stronger antibiotic, she was fine and hasn't had ear infections since. This was quite a few years ago, so I don't know what the antibiotics are now, but if your pediatrician hasn't looked into a stronger antibiotic, you might want to ask about it. It could save you the hassle of going through all the other testing, etc, to rule out other issues.