I have the same problem for about 6 years and I've been told by doctors and dentist that it is called "Geographic tongue". They say its nothing to worry about, but when there's pain involved, its something to worry about. I did some research of my own and found that it occurs with people who have major food allergies , and don't know it. Also, can be fungus and over growth of yeast in the body. I also found out that hundreds of years ago, Egyptians used to diagnose eachother by how their tongue was looking. They actually developed an instrument, similar to a spoon, to scrape bacteria off their tongues throughout the day. I notice that mine will flare up if I'm eating too much sugar, citric acid , and salt combinations. There are other countries that still practice diagnosis by looking at the tongue, afterwards, it usually requires some hebs and cleansing.