
Eclampsia is shortage of Calcium in the blood, which will cause the heart to fail eventually. Signs to look for is stiff movements, shivers and trembling, and more or less any behaviour you wouldn't expect to see in your bitch. Veterinary treatment is then imperative, otherwise the bitch might die.
This (eclampsia) isn't very common, although every breeder should be aware of its' excistence, and allways on the lookout for sympthoms. Should eclampsia set in, it is most common when the bitch is having a large litter, and is in full lactation. I seriously don't think this is what has happened to your girl, as she would have been very ill by now. I rather think she's digging to relieve herself of the tension from having the uterus contract, and the pain it causes her. Try putting a warm towel on her tummy, and maybe a very gentle tummyrub when she's feeding her pup, as feeding will increase the contractions. Nature is wise, is it not?!