Irritated one side of the mouth?

Not sure if it's the gum or teeth. It seams to be irritated between the gum line and between the teeth on the one side of my mouth. no pain. one bottom tooth feels soft on the back part of the tooth and inbetween the third and forth teeth soft and as if the gum line is separated from the tooth. The tooth has a swelling feeling and soft feeling. The tooth does not feel hard like the normal feeling. What can this be if exrays show good gum and tooth and no signs of infection? I cann't be the only one with this mistry problem. I hope.