Well kitha1215, I need a few more details about what you observe as wrong, since the pic isn't very big. But off the bat I'd say, it looks like its in a pot that's too big for it. Have you potted up recently? Being in to large of a pot can be bad for your christmas cactus, esp. during the winter months, when a good watering in too large of a pot can be very detrimental--b/c too much wet soil next to the roots can cause rot as the roots are unable to absorb all the water surrounding them. It appears to be in a 6" pot. I would down grade to a 4" pot. Christmas cactus actually seems to enjoy being a little root bound, and will concentrate almost exclusively on root growth until they feel they've filled the pot to they're liking. It's best not to re-pot in the winter months if at all possible--spring is best time to 'pot up' as it gives you plant lots of time to fill its new space--but as we're down sizing our pot and you seem to be worried demise is imminent I would repot into a smaller pot right away. Christmas cacti are actually a jungle cactus and appreciate a good drink every two-three weeks or so in the winter (at least here in WA). I plant mine in a bromeliad mix with a little extra vermiculite for drainage. But if you are worried about overwatering (maybe you like to baby your plants) I would definately go with something with good drainage, poss. a good quality cactus and succulent mix. I also plant most of my jungle cacti in terra cotta as they breath better, I find. When you repot give your plant a good look, if you see any bugs (seem to get spider mites quite easily (little cobwebs--mites are so small that if you can see them easily you got it pretty bad)) rinse off the plant and roots and give it a good dose of Safer houseplant insecticide (it has a aerisol like sprayer on it and I find it easier to use)--reapply as needed. Then re-pot in sterile potting mix give it one good drink and try not to water it until it actually appears dry all the way through (2-4 weeks depending on conditions)--to keep from having the same issue again. Also, as a last ditch I would pinch off a couple of leaves of the new growth on the ends--to clone your cactus if it looks like it won't continue (christmas cactus are super easy to clone take the leaves you've removed and push the pointy end in some potting soil (smaller pot 2" is best) water once and don't water again until you can tug and feel roots formed). Hope this helps!

When I look at the photo - maybe the soil was too heavy/organic. Succulent plants need fast draining soil, containing a lot of inorganic fraction (grit, river sand, perlite or similar materials).

Rachel, it's very hard for me to make an assessment when I am not physically there to examine your plant. I don't quite understand what you mean by soft but not overly. I see that your last picture you had lost a couple of stems, so perhaps if its really rot setting in the base, you need to catch where is the rot happening at. If it's right under all the stems towards the roots, you are better of cutting off as much rot/brown portion as possible until you see healthy green stems, and try to root the cutting as best as you can. At this point, you can try to snap 1 or 2 healthy cuttings at the tip end towards the base. Always let the cuttings dry up and callous before their to root them in new soil. And also make sure when you snap them apart, the stem must be close as to the root base as possible, if you can snap some roots with the stem even better.

So sorry to see your plant in this condition! Did you water it to often? Did you check the roots? Guess they are rotten. Don't think you can save the main plant :-( But try! Repotted it in the little bit smaller pot and don't over water it.