For what it's worth Lacey has had 2 false pregs out of 3 heats so far. She didn't gain much weight if any, but she did nest and had some "milk" (it was clear). Her breasts didn't get mastitis or anything, just noticed she had slight "bags" and I checked for milk.
The first couple pics make it look like she may have mastitis but it could just be the angle.... check her breasts for milk, redness, ect.
For it to go down that fast.... well it shouldn't go down at all LOL until pups are born, if preg.
It STILL could be false, I sure hope so for your sake and sanity!!!!