My gums are swollen directly above an old root c...?

I was told by a dentist I saw a few years ago that I have "hereditary hyper-decay disorder." Basically, although I take extraordinary care of my teeth... they get cavities all the time. I have mutliple fillings on every tooth, 4 root cs, two molar extractions, and need two more molar extractions. I had a root c on an upper molar about 2-1/2 years ago. I have never had it crowned (I know that I need to have this done) the molar below it was also a root c. I never had it crowned either and the tooth has rotted to just one small jut of tooth. I also grind my teeth at night, and have ground this tooth piece into the filled portion of the molar above it... now I have swollen gums on the outter portion of this molar... it feels almost like a liquid filled bubble, and is sensitive to touch... it feels like I am pushing the molar when I feel the swollen gum with my fingers. At this time in my life, I just do not have the funds for a dentist visit. Any suggestions?