Ive had headaches while sleeping since having sinus surgery a yr. ago. getting up every 2 hrs. gives me some relief. why?

Thoughts: Seems to me there may be 2 possibilities. 1) headache is not associated with sinus problem, but may be due to not getting enough oxygen while you are asleep. This can be due to sleep apnea and a sleep study is required to diagnose. Waking will improve oxygenation. 2) sinus issues have returned, but oxygenation still improved upon waking and breathing through mouth. Either way, evaluation needed