When you wake up, look in the mirror and stick out your tongue. If there is a line or crease down the center of your tongue you are dehydrated. Drink 8 ounces of water every thirty minutes until your tongue is soft and flat.
Do this before bed so that you go to sleep fully hydrated. Do you wake up with your tongue still soft and flat? Are you feeling better? If so, yes, that was your problem.
If not, you should really see your doctor. Treating sleep apnea can have such amazingly positive results; make it a priority and find out how much better life can be.