I'm not sure of the answer - I'm no expert. Hudson's our first bully (and our first dog), and he's at his 55 lb mark. The vet said no more weight and switched him to adult food.
It sounds like he's close to standard weight, which I believe is 50-55 lbs. But you can always check with your vet for a final call. Ours encouraged us not to get stuck on the "big" bulldog sterotype.