Singaw or Mouth Ulcer

I don't know what could be causing it but this December I had a very bad mouth ulcer or also known as "singaw." First was before Christmas I had one on my tongue. Its so bad because its on the side and it hits my teeth when I try to talk or chew. It was really a big relief when it disappeared however I had another very bad one after Christmas. I noticed that the side of my upper right gum hurts, only to find out there is another "singaw."  This time its one on the gum and one on the cheeks opposite to it. I'm not sure if its causing it but I feel the tooth near the gum with mouth ulcer hurts a little bit too. I'm still hurting as I write this but anyway this doesn't stop me to enjoy the food this Christmas holiday. @_@