I had the exact same thing. I asked the pharmacist about it and she said it was a fungal infection and to use Clotrimazole, an atifungal cream used for athlete's foot. I bought some and used it only twice. It hurt and I began to feel right away it wasn't going to work. I asked my family doctor about it. She said it was caused by stress (I was going through a lot at that time). She said we would try Triamcinolone Acetonide. It is a dental paste actually made to use on lesions inside the mouth. It feels grainy and that is annoying, but it worked for me. It takes patience, it took a long time, probably about 3 months using it twice a day. I hope if you try it, it will work for you!