If you have had several experts tell you that its nothing to worry about, then you are faced with the difficult task of accepting the diagnosis. I think there is a sticky for it. There may be something environmental causing this such as a consistent food that you eat that causes this. For me, if I eat anything that is slightly hot, then I will shed the entire roof of my mouth, and I hate it when it happens. Acidic foods can do this also, or things with abrasive textures.