fps issues need help

[Gwelade]

hey guys, my pc is only 2 year old and here its build

cpu i5 intel core 4570 3.2 ghz

16gb ram

ssd128gb and 1tb hd

GTX660 geforce nvidia

and 750 watt power

Why I'm having low fps? i mean like i have all settings at 1 and still my fps its like 40-45, and in battles and pvp drops  to 20, anyone can give me  tips what i have to do???

shouldn't i with this pc have good fps at high settings? instead of low fps at lower settings?