I am trying to diagnose what these small white discolored circles behind my sons ear are?

?Pityriasis: Patchy skin lesions can be hard to diagnose (especially without seeing it with my own eyes), but it could represent a form of tinea ("ringworm") or a condition known as pityriasis alba which could be due to yeasts on the skin. See http://www.dermnetnz.org/topics/pityriasis-alba This is a situation where review by a family physician or a dermatologist may be helpful.

Let us see.: Your best bet on this forum would be to pursue a virtual consultation with one of us. You can take a picture of these circles and upload it during the consultation. That would be your best bet, besides having them evaluated locally, of course.