Plateau.

My cousin Karen (that I live with now) and I have started our major weight loss plan this month.
This week I have really started to plateu. I lost five pounds in the two weeks before, so this week I stepped it up (Added extra 10 minutes of cardio and been eating perfectly) and nothing! Grrrr, plateau's are really discouraging :(
Anybody have some good pointers of shortening, or avoiding a weight loss plateau?!