I agree with Tirzah. When your dog begins to dig they are typically trying to build a "nest" to sleep in. When he/she sees you settle down your dog wants to sleep there with you. I guess you are not quite the shape that your dog wants so he/she is trying to make you more comfy! Ha ha!
Sometimes I swear my dog digs on me because she wants me to move out of the prime spot in bed. :)
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