Congrats on your awesome progress! The closer you get to your goal weight, the slower you're going to lose. I'd recommend having your body fat tested b/c that's a better indicator of health vs. a number on the scale. Also be careful b/c if you're not eating enough for your activity level, that can make weight loss more difficult.
Here's an article about maintaining your weight that you might find helpful: www.sparkpeople.com/resource/wellness_arti
Hope that helps,