I bite my lips, the skin around my fingers, my cuticles, and my fingernails. I’m really bad about it. I even broke a tooth from nail biting. I never have any of the white part of my fingernails. The only time I have managed to stop was when I was sick with digestive stuff and I worried that getting bits of nails into my tract would make things worse. It resumed when I was healed up. I have no idea what causes it or how to stop, but I sympathize!