With the brain fog and nausea, I most definately suspect you had a "stealth" sinus infection up there. It is good you are finally getting all that nasty gunk out. I know how horrible it is, but hang in there. When it is resolved, I bet you'll have more energy than before. You might want to take some antibacterial supplements like oil of oregano, grapefruitseed extract, garlic, or caprylic acid. And definitely irrigate.