Snakes don't typically "go" (either urates or feces) very often...it's not a daily thing, & often not even once per meal eaten, it can be less often than that & still be normal.
The bulge does suggest a possible blockage...he needs to stay hydrated (which it sounds like he's doing with help) & I agree with bcr229's post above ^ ^ ^ that now
is NOT the time to feed him...wait & see what the vet thinks. It could be something else too, of course, but with any luck, the extra hydration might just let him pass it.