Bleeding and moving gum?

When I was brushing my teeth, I noticed one of the bottom ones next to the front two was bleeding. I touched it with my finger and it moved down a little bit, not to expose any of the root but it moved more than any of the other ones. Could this be gum disease? Or have i just brushed too vigourously? Any ideas? I'm petrified of losing my teeth and also petrified of the dentist!!!