I think you might have had problems with your teeth/gums and they're very important to the rest of your health. Get the diseased teeth problem out of your mouth and some of that stress on your body and you got better but then if you didn't change anything permanently (how and what you eat, sleeping habits, etc.), then things will go back to normal.

http://www.ada.org/public/topics/ora...gumdisease.asp

I would check with your doctor and have him do a checkup, make sure there isn't some other problem lurking that is causing your memory, focus, and sleeping problems.