Have you figured out your BMR and total calories burned and then adjusted it as you have lost weight? If not here is a website you can do so:
http://www.goodhousekeeping.com/health/advice/calculate-calories-bmr
Go by that and also maybe up your exercise. That's all I know to tell you...hope it helped some! Good luck!
Here is a very in-depth, no-nonsense approach to overcoming a plateau:
http://www.answerfitness.com/208/weight-loss-plateau-tactics-overcoming-weight-loss-plateau/
It recommends everything from changing your exercising routine to calorie cycling. It's a great article and offers several different paths to breaking the plateau.