Hi Stephanie,
Congratulations!!!! You have done an excellent job losing weight. Here are two tips that should get you over this hurdle.
If you've been following the same activity routine - mix it up. For example, if you typically walk switch to biking or swimming. This works new muscles and can push you through a plateau.
Add strength training - If you are not currently building muscle via weight lifting or other strengthening routines, definitely add this to your routine. The extra muscle mass will burn more calories and help you shed these last 20 pounds.
All the best,
Lisa Nelson RD
Lose Weight the Healthy Way