Thanks for the additional information. I really appreciate it.
With an unaltered female, the first thing we think of when we hear that she's lethargic and sick is pyometra.
The term 'pyometra' means pus in the uterus. This pus formation in the uterus results from infection, hormone imbalance or mucous buildup inside the uterus. Most dogs and cats suffering from pyometra are presented because of loss of energy, vomiting and/or diarrhea, increased thirst and poor appetite.
Pyometras can be either open (where the cervix is open and there is drainage) or closed (cervix is closed, no drainage, and dog is very sick). If your dog is licking her vulva I suspect it is open, but there is always the chance it will close. If she's not paying any attention to her vulva at all, then it's probably closed. From your description of the fact you're not seeing any discharge and there's no noticable blood in the urine makes me feel that this could be a closed pyometra...which, unfortunately, is more dangerous than an open one.
With an open pyometra, you probably wouldn't see anything on x-rays as the pus is draining out. An ultrasound would likely show a thickened uterus and fluid, but the x-ray isn't that good for detail like that. An open pyometra also might not show any changes in bloodwork, particularly early on. With a closed one you would expect an increase in white blood cells, but not necessarily early on, and of course, the only way to know for sure if she's got an increase in her white blood cells is through blood work at the vet.
My suggestion is to get your girl to a vet as soon as you can. If she does, in fact, have a pyometra and it is left untreated, it could very well rupture and kill her.
I hope this helps.