Question
my cactus is a trichocereus camarquensis and it only seems to be growing at the top which is making it wobbly as its getting bigger than the bottom part.  Any ideas what I can do??? thanks  

Answer
Sorry I am so slow in answering. I ma not very familiar with is cactus but believe  some are grown specifically as a hanging plants.  You could cut it and start a more compact plant, being sure to let it callous first and then put it in damp sand. Than you can also see what happens to the bottom. It may develop some arms. I wouldn't do that till Spring.  In the mean time stake it so it's not wobbly and make sure it's in the right size pot.  For a columner cactus the pot should be 1/3 the size of the plant.  If you stake, remember not to water till Spring.  It is dormant now and doesn't require water till March. Before you do anything do some research on the computer to determine growth characteristics of the plant and then decide.

If you send me a picture and tell me how large it is perhaps I can be of more help.