If she is far enough along to do so (28 days), get an ultrasound. And just for peace of mind, have your vet check her over also. It may be that she is feeling pressure on her abdomen or diaphragm, or there may be a problem. It's always best to know what's going on if you see any unusual behavior.
The first litter she did not know what was going on.....this time she wants
to make sure that YOU KNOW what's up because SHE KNOWS......SHE IS HAPPY AND VERY PROUD OF HERSELF! Enjoy and talk to her about her pups....of course
rub her belly and she will (talk) even more.