I went through the exact same thing. I tried everything under the sun, but nothing seemed to stick. Eventually, I stopped biting them—well, maybe not entirely, but after about ten years, I started using a chewelry piece instead. If you can't find a way to keep your hands busy, try finding something for your mouth to do, like chewing on something. Now I just need to stop picking at my skin and then I'll be golden. 🙂