You know, I believe there are things you can buy to paint on the nail to discourage you from biting them. I'm not sure where you would find these but I seem to remember hearing about them at one time. I would assume the taste would not be pleasant, which is what would keep your fingers away from your mouth.
I have this same habit, have had it since I was a child, and have found the only way to keep from biting and picking at my nails is to wear fake ones. They not only can't be bitten off, but my nails are so pretty I don't want to touch them. I've been wearing them for about a year and a half now and find I'm showing off my hands every chance I get instead of hiding them in my lap. I have a friend who's the same way, she's forever biting her nails but when she has the nails on, her hands are beautiful and you don't see them so much as near her mouth. May be that's the only solution for you, too.
Good luck, and let us know what you decide
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