I know my Westie can get a little cranky if he is laying down and my son (now a teen-ager) accidentally kicks him with his foot on the couch or some such.
Could that have happened?
Seems like you have gotten a lot of good advice.
Here is a gentle, everyday, training program (or really way of life) that can help reinforce who is in charge here (you!).
Dog Training: Nothing in Life is Free : The Humane Society of the United States