My JR cross is the same, I only have to say "what have you been up to ?", in a normal voice , her tail goes down and she curls up in a ball.She was a rescue dog and had a family ownership with children who tormented her, then an old lady who used to smack her with a cushion or a newspaper, and then myself.
I have had her for 5 years now and have never hit her or anything like that but she is very nervous indeed.
I give her Bach's rescue a few days before Nov 5th, it does seem to help along with all the extra cuddles.