Borrow a known "good" monitor from a friend or family member and swap it in.. If the borrowed monitor works correctly, then you'll know the culprit.
Still, it might help us more if we knew more about your computer.. Operating system?, monitor type?, and whether you have tried installing video drivers on your machine, just to make sure it's not a video card issue.
Hope this helps.
My monitor is looking really bad it looks matrixy(?). I don't know what is up with it, I bought it a year ago. Could it be the monitor or something else?