dear suffering man:
one...spend the mone and see at least three doctors on the subject
two...keep a log book and see if you can find other factors as you may have HAY FEVER or ALLERGIES...
three...find a book called: sinus survival
I am a pilot...terrible time living in the eastern US as I had many allergies...ended up taking weekly allergy shots (injections) and it helped a great deal.
AFRIN nasal mist should be on your person if possible for all flights in case of emergencies...but beware the rebound effect which will make things worse in the future.
also, try very long hot showers to allow some relief from swelling of the nasal passages.
I had to consult doctors in Boston, San francisco, and Washington DC before I found my cure.
Good luck...are you French?