It sounds like she may be in labor. I'd love to have a puppy. My Yorker passes away last year at age 17.
THAT is not just close .. But, I'd say she has already started labor.
Hiding and wanting to be alone all the time are one of the biggest signs yet that your dog is due anytime now.
To be even more sure,
Your dog's normal temperature will be between 101-102 degrees. Take her temperature frequently, and as soon as you see it drop to 99 degrees or below (and make sure that you see this same reading again after at least 12 hours) then you can be sure that your dog will deliver in the next 24 hours (or 48 hours at most).Since your dog is so close to giving birth now (exciting times, I know! :D) you're going to want to do some reading because there are some stuff you should know about: http://ultimatehomelife.com/dog-pregnancy-gestation-101-how-long-are-dogs-pregnant/
This question posted four days ago, I hope she has had those puppies by now. So how many and how stinking cute are they?