picking and eating

I'm going to be brave. I've heard that I'm not alone in this but it seems like I am sometimes. When I pick and bite my skin, I eat it. I have NO idea why or when I started this. It's more embarrassing than the picking because people can totally notice me gnawing away. I get so anxious and nervous and can't help myself. Have you heard of or seen this? Or do you do it too?