Skin chewing

As long as I can remember, I have chewed my nails, my toenails, the skin around my nails, and the calluses on both my hands and my feet. Once I have chewed what I can get with my teeth, I will take fingernail clippers and clip off bits of skin on the entire area until it is too raw and I can't get anymore. Then I keep pulling at it over time, sometimes until it bleeds. This is most common on my feet. I'm not sure why I've come to do this. Maybe it's from anxiety, maybe it's from stress. Maybe it's just to have a secret I can keep to myself and never let anybody find out. It sucks though, constantly hiding my feet and tips of my fingers. What do you people deal with? What causes it? How do you fix it? I'd love to have people like myself to communicate shamelessly with. Please feel free to share stories :)