The hard part is determining the cause of the problem. It could be a viral illness. It could be part of an ear infection or even a sinus infection, which could require a course of antibiotics. The easier part is what to do. I would speak to your physician again and possibly have a CT scan of your sinuses if this persists. The specialist most qualified to deal with this is an ENT specialist.
Have you Dr. check for Mono and or Epstein Barr
I had and still have the same problem - it seems to
come back every time I exhaust myself
Good Luck!