They're quite individual in terms of when and how much they show, I find. But that is really quite round for two months to go!
My one girl, Buffy, always gets absolutely ginormous, whether she's producing 2, 3 or a singleton. And Anya always looked ready to pop early on then held on to be the very last to lamb

.
The Zwarties here apparently don't show much at all until very close to lambing. My 7 fleece girls are all nicely round (well, apart from the two earlies who lambed today), but the Zwartbles, who are due 10-14 days earlier, are barely showing anything.