My 12 Year Old Son Has Been Sick Since Feb.

my 12 year old son has been sick since Feb. 19. I took him to the doctor on the 20th they said strep throat, Took him to urgent care on the 26th they said he was getting over the flu, by the first he was still running a low grade temp so I took him back to the doctor, they said fluid in the ear and possible broncious. He still does not want to eat and has a low grade temp on and off and has very little engery. What can be wrong.