Your dog seems to be in a lot of discomfort. At her age it could be anything from organ failure to frail bones. I would make an appointment with your vet and get a physical examination for her to find out exactly what the problem is. Waiting longer could make the problem worse.
I hate to give this news, but it sounds like some form of organ failure. I assume that she isn't lying down because it hurts her to. You need to take her to the vet to see if there is anything that can be done.