centos linux server is very slow, named is using too much cpu

I have a vPS linux server with CENTOS 6, mysql, drupal 7. the website will barely load and ssh commands take a few seconds to show on the screen. this issue has been happening for 3 days. named is the process with the highest CPU usage. /proc/loadavg is showing an ok load, it is not too high, so there is some other issue. I need someone to investigate and fix asap