What could be causing this someone answer?

for the past 2 weeks ive been dizzy not like spinning just out of it dizzy and i have had headaches with lots of phlegm my headaches come and go and i have lots of phlegm when i wake up its not major its just really annoying so what could it be and i went to the doctors and he made me get a sinus x-ray i was fine but ive been stressed out a lot lately