Some plants grow smaller than some other plants. By the sounds of it, yours sounds like an Indica dom. strain, which tend to grow short and thick. Having a short plant with tight internodes is a good thing. Things will stretch big time when flowering hits. The top will stretch a good inch every 24-48 hours for a good solid week when flowering begins. Keep things small now, or the end result will be stretched out, lanky, light and wispy buds.

Good luck.