Screen Size too big

When I start the game I only get a portion of the screen, the rest I cant see because it's too big. By too big I mean it's like it's zoomed in and a chunk of the game is all I can see and the rest is offscreen. I tried changing resolution in the config file but all it did was change the size of the window itself and not the game, and therefor cropping out even more of it. Any idea how I can fix this?