Very poor performance on CS:GO

AshyCFC

Honorable
I understand my PC isn't a world beater or anything special but my performance in CS:GO is unplayable at any setting level.

Here's my spec

FX-8320
HD 7870 2GB
8GB RAM

Any idea what's wrong with it/what I can do? I play @ 1080p though have tried various resolutions/graphics settings.
 

AshyCFC

Honorable
PSU is an XFX 550W Core edition and actually I've been testing it recently and didnt have any trouble in my last game (thoguh i'm on essentially lowest graphics quality)

Other games are all fine, I think CS:GO may be fixed but will take more matches to test.