Well I think enemas are the way to kill worms that can move all over. Lemon juice enemas especially, but other things. Kefir really does some nice work in an enema - but the entire gut has to have a changed environment.
I am not sure if the giant worm you refer to is a tape worm, but some Tapeworms are removed surgically because they can be so large.
I have also heard that some herbs do nothing to get rid of large parasites (or they belch as you say) and so they need much more aggressive things- sone have used silver, mms, msm, DE, flora, borax. etc. It can take a while to change the gut environment, but it can be done.