A number of things could be wrong. You need good diagnostic tools to find out what's up. The best reptile vet in the world could not possibly tell you what is wrong with your snake based on this description alone. A microscope (or a good reptile vet) is a snake keeper's best friend in situations like these.
If this animal is wild caught parasites are pretty much a given. To find out what parasites are present, get a fecal exam. Regurging is very often (but not always) associated with a heavy load of protozoa in WC gabbys. You could guess and dose the animal with 50mg/kg metronidazole (Flagyl) every 3 or 4 days for a few weeks, but if your guess is wrong then you'll have stressed the animal and worsened its problem instead of solving it.
You could be looking at anything from cryptosporidia to neoplasia, and without some diagnostics you won't have a clue how to properly treat the animal. A fecal exam is a good place to start identifying what is actually wrong with the animal so you can begin the appropriate treatment.
If your snake isn't giving you any fecal matter, do a fecal wash. Get the snake's head and a chunk of its body in a tube, leaving the back end free. Flush a small amount (1% of the animal's body weight or less) of sterile saline gently and slowly up the cloaca using a red rubber catheter tube and a syringe. Massage the fluid around and then GENTLY aspirate it back out with the catheter. Expect to recover less than half the fluid you put in. Yes, the plain saline they sell in drugstores for contact lenses is fine for this use. Bring the aspirated liquid *immediately* to the vet for examination. The fresher the sample the better.
While many vets won't see hots, I don't know any who will refuse to see a fecal sample while you leave the snake at home.
If the fecal doesn't give you an obvious culprit, a tracheal wash would probably be your next procedure, looking for lungworms. This is a somewhat more advanced procedure that I would suggest be done only by experienced care providers. I've done this on conscious patients but it is often easier, safer and more comfortable for the snake under short duration anesthesia.
Some helpful articles are at the link below.
Vet care for venomous snakes