For the past four days i've been feeling under the weather, sensations of vertigo, occasional light headedness and slight nausea. I can't think of anything that could be causing it - except that I am a week into wearing an oral retainer for my top teeth. My teeth have shifted greatly and the retainer is still quite tight when I replace it after it's been out of my mouth. Is it possible that my sinuses are being affected and thus giving me that feeling? Or should I assume that's not a possibility?