Many of the dens require a chilling period in order to initiate spiking, Kelly. Can't say for certain that this is the case for yours but that may be the problem or at least part of it. Furthermore, you may be being too nice to your plant. Again, it is common for most dens to enter into a dormancy period before flowering. No dormancy, no flowers. During such a dormancy period watering is greatly reduced (in some cases completely stopped) and no fertilizer is given. Again as I already mentioned, many desire cooler temps during this period as well. If conditions remain "too good" (plenty of water, fertilizer, and warm temps) the plant does not go dormant and instead just continues to put out growths.
Now that is all "general" tendencies. Never having grown any of the antelope type dens myself, I cannot say anything more definitative. Hopefully someone with more experience in this department will chime in. Btw, do you know the plant's name? That could prove helpful.