Garry's Mod Shadow bug

[stiggy12]

Hi. My Gmod has been having a really weird issue with its shadows mainly edging shadows like those in the corners of walls. The problem is the shadows move around and don't sit in the correct place and sometimes they move with my players look.

Can anyone help. Thanks in advance. 

http://prntscr.com/4ct7op <<<-- screenshot showing issue

http://uk.pcpartpicker.com/user/12stiggy12/saved/rNcMnQ <<<- part list to show system specs just in case the parts are the issue.