FPS issues with GTX550 Ti

Hi! i havea home built computer, im running 16gb ddr3 ram, an amd fx 6 core processor, and a nvidia gtx 550ti. When i built it i was able to run WoW at 60 fps on ultra a pretty constant rate... now however i am struggling to get 20-30 out of it... i'm wondering what would cause this and what i can do to fix it. I have gotten mot up to date nvidia drivers. uninstalled ALL of them and reinstalled and messed with most of the settings in wow, as well as deleting the WTF and casche ( even dropping to high settings from ultra barely makes a difference it just constantly sits at 30 then) Please give me any ideas that might help fix this issue.
Thanks!