I have a "U"-shaped spot on my tongue. It is red in the middle and surrounded by a white boarder. This is the fifth one I have had. It is on the top/lateral side of my tongue. I only get one at a time but they are always in the same area. The ones I have had in the past were more rounded and tend to get large (1 cm). I have had this condition for almost two months, no other symptoms. It is not painful at all! They usually last for a week and then go away, and a few days later another one will appear. Any idea what this could be?