My guesses based on the photo would be Impetigo or Ringworm, however, if this infection is not responding to the antifungal medication I would lean more to the possibility of Impetigo. Reconsult your physician and inform him/her that the medication is not working. This is probably not going to clear up immediately from
the looks of it.
How long have you been taking the antifungal medication/"thrush pill"? How many pills are you supposed to take?
I would recommend not applying ANYTHING on it.
if he says it's a yeast infection, i know this is going to sound very crazy but it works on them all. go to the store and buy monostat or a generic form of yeast med. for a womans yeast infection, but make sure it's a cream form, and apply it to the area and see if that helps you out at all.