I can't see my comments

I’ve been told by several people that they’ve left comments on my blog however I am not able to see any at all!

I’ve tried the following:
– disabling the discussion settings
– tried to check the “discussion box” under screen options under the page section but I don’t have the ‘discussion’ box showing as an option at all.
– I’ve also changed the theme several times

None of these have worked.
Can someone help me? And why don’t I have a ‘discussion’ box in my screen options?
Thank you

http://wordpress.org/extend/plugins/comments/