are you talking about pinky rats? how old is your snake? if it's a couple months old, it can either eat an adult mouse or rat pup. One reason why your snake hasn't pooped is because he's absorbing and using everything that he can from the carcass, leaving little waste behind. I'd bump up your prey size a bit. They can handle prey that's as big as the widest part of your BP's 'stomach'.
i am feeding him pinkie mice- thats what they said at the pet store to use untill i was sure he was a good eater. (which he is) an adult mouse is a little fatter then the fattest part of our snake.- can i get a juvenille mouse from petco/petsmart