Could be stress response, but the thin shelled egg and the egg yolks found on the puppy pads is concerning nonetheless. I would give extra calcium for a 2-3 days to see if that makes a difference and allows her to form a shell.
It's always good to make oyster shell available free choice, but...
Do you have any calcium to give her? You can give Caltrate or even a TUMS for a couple of days to see if that hardens the shell up.
It sounds like she's having some reproductive problems, hopefully it's just a glitch and things will work out. Feel her abdomen for any bloat or fluid.