Not even sure what cactus this is. I somehow wasn't interested in it's classification when I got for Christmas at age seven. It's had what looks like a rotting trunk for as long as I can remember. We thought it was dead, but gave it the benefit of the doubt and moved it to a larger pot and it grew. Sometimes it seems to glow brighter and appears to be thriving well. Everything but the trunk, and you can see that I've used a make shift cane to support it. Otherwise it falls over under it top heavy weight. Can any anyone explain what's going on with my cactus and if there is anything I can do?