
Hopefully someone with experience of this will be able to give you some advice but I fear that most will be likely to respond tomorrow. I may be wrong but I think I read a thread a while ago where the bitch lost more than one pup over the space of a week and then went on to carry the rest of the litter to term and have live pups.
Try to stay calm and keep your girl as relaxed as possible. It may be that she has just shed the empty sack. I am assuming that you have spoken to your vet and that is why she has been put on antibiotics - or was she one those already? If so - what for?
Perhaps you could have her re-scanned just to see what is gong on as long as it doesn't stress her out.
Will be thinking of you both...