I Had a Cavity and It Started Chipping Away Now All Thats Left is Up in my Gums?

I am terrified of the dentist. I noticed a small cavity on the side of my top right tooth all the way in the back (not my wisdom) about 4 years ago. I never went to the dentist. It's never hurt me its a little sensitive when i brush or bite on something hard. The tooth started chipping about a year ago. and now I feel like my whole tooth is gone. I feel the hole up in my gums where it suppost to be. I feel little shards like the root and more tooth is still up there. I am curious on what will be done.