I was in a Cessna 206 headed to Oshkosh. Our pilot had planned to fly Eastbound at 17,000ft to avoid an air current. We all got nasal cannulae for supplemental

I was in a Cessna 206 headed to Oshkosh. Our pilot had planned to fly Eastbound at 17,000ft to avoid an air current. We all got nasal cannulae for supplemental oxygen. We departed at 3AM, and following takeoff I immediately fell asleep. I woke up somewhere around 14,000ft, dizzy and confused, and realized I hadn't put my cannula in before falling asleep. I fixed this, and within a minute the brain fog was gone and I proceeded back to sleep. Then we hit turbulence, which in a small craft like a 206 means you occasionally whack your head on the ceiling. Couldn't sleep through that.