I assume you are keeping him on aspen? Sounds to me like he swallowed some aspen along with a meal? Do you feed him in the cage without putting down something
like a box lid so the aspen doesn't stick to the damp prey & get swallowed? That's what you SHOULD be doing, but now, he is likely in pain & yes, should be SEEN by a
qualified herp. vet. Not all vets treat snakes...they need special training & experience to do a good job on reptiles like snakes. This is NOT something YOU can take care
of by yourself, & delay could mean your snake won't survive. Aspen cannot be digested by a snake...their stomach doesn't have the right enzymes to digest plant material-so if he ingested very much, it can get stuck, undigested, and block him up so he cannot defecate. Also, even small pieces -IF sharp- can perforate his intestine. I know many use aspen with apparent safety, but I don't, & never have liked it for snakes.
You (your parents) might try this to find a vet near you:
http://arav.site-ym.com/search/custom.asp?id=3661
About the only thing I can think of that you could try at home is a soak in lukewarm water, not deeper than the snake is tall (about an inch or less) & see
if it helps any...it might help him to hydrate enough to defecate. Does he seem swollen above his vent (cloaca)? (like he needs to "go"?)