I have had no cavities or anything done to my mouth. In the left side of my mouth my one tooth in the back hurts when I touch it. Then when i press on the gum above the tooth behind it that hurts as well. Also, my cheek has some pain in it to when i press on it. The only explanation I have to describe this pain is it feels like these two teeth are being pulled tighter and tighter. I can not chew on this side of my mouth, and my dentist keeps telling me he can't find the problem because nothing is swollen. Do I need a root canal?