stop feeding your boa. the next thing you're going to have to do is take it to the vet. if it's regurged a couple of times, it's probably dehydrated and needs some serious attention. after you've taken it to the vet, don't feed it again until about 3 weeks have passed. then, when you do, give it the smallest pinky mouse you can find, something that won't even make a lump in your boas belly. then, wait another 3 weeks and do the same thing. another 3 weeks and the same thing. if it has kept those 3 meals down, you can step up the food size JUST A LITTLE BIT but don't feed any more frequently and NEVER feed a prey item bigger around than the largest part of the boa until it's over a year old and larger than 3 feet. after it has kept several meals down, you can feed a little more frequently, but IMO, there is no need to. boa keepers in general feed entirely too often and if you wanted to feed one prey item every 2-3 weeks, that would be just fine. matter of fact, that's about how often i feed and my collection grows at a NORMAL rate and they're all healthy and robust animals that should live a long life.
the next thing you should know is that your husbandry needs to be checked over. purchase a temperature gun. you can get them now for about $30 or so and it's the very best investment you can make for your reptile collection. if you have a dog or a cat or you have a couple of extra bucks to spend, get one with the red laser sighting and you can drive the dog or cat crazy with it. most people don't realize until they get a temp gun just how inaccurate their temperatures are. many people overheat their animals by an extreme amount, which can cause regurging and many people do just the opposite, which can also cause regurging.
you should also sterilize your enclosure with a 10% bleach 90% water solution and just for good measure, treat preventatively with provent-a-mite and then switch to a paper towel substrate or newspaper. you also need to provide a couple of hides in the enclosure at various locations so that the boa can thermoregulate itself and feel safe in any spot it chooses. your temp range should be between 80-86/87 just to be safe. you also need to get a digital hygrometer that will check your humidity. you need 60% or higher for optimal health. place the hygrometer in various locations around the cage to get a good idea of what the ambient humidity is and work from there. if you need tips on getting humidity up, do a search on this forum for "humidity" (or possibly the old forum) and you should find enough to keep you busy for hours.
that should be enough to keep your boa alive and eventually get it healthy again. remember to take your boa to the vet, it probably needs to be rehydrated. soaking isn't going to work for your animal because it sounds like it needs something more substantial. some baby food fed through a syringe may be a good idea. and be sure you take it to a REPTILE vet, otherwise your vet may be completely clueless as to how to properly nurse your animal back to health (but they probably wouldn't tell you that).
good luck and let us know how it goes.
jb
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Jonathan Brady
My Kingsnake Photo Gallery