Anytime I press the X (A) button on my controller the game try's to add a second player. It also happens if I press the start button. Is there a way to deal with this?

edit: misread your post, I apologize.

This is just a wild ass guess (I don't play with a controller), but is it possible your X (A) button is mapped to the multiplayer menu? Can you go into the key mapping settings and re-bind it?