Those are really nice mollies btw, kinda short though, I almost think they're platies.
From the pics, I'd say they're pregnant, mollies usually are anyways when you buy them. As long as their swimming is fairly normal i.e. no trying to swim down but floating upwards, no sinking to the floor, etc... I wouldn't worry about any kind of bloating.
Deffinitely get a breeder net ready (i suggest those over those plastic ones) and put in some J moss and you'll get a really high survival rate with the fry.
Good luck! HTH