If your regular vet can't see anything amiss in the spine xrays, but suspects something with the spine, ask to have the films referred to an orthopedic specialist for evaluation. The specialists often can see things on xrays that aren't readily apparent to a regular vet.
Good luck tomorrow! I hope you get some answers and get little Munch back on the right track!
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."