Yep, this happened to me too. My weight loss REALLY slowed down as I got closer to my goal weight. Things to try:
1. Really scrutinize everything that goes in your mouth for a week, sometimes calories can sneak in
2. Increase the intensity of your workouts. Walking is GREAT exercise, but it might not be enough at this point (you are conditioned now! you have to do more to affect your body the same way!)
3. Zigzag calories (up a little bit one day, down a little bit the next day, keep the body guessing)
4. I know this sounds crazy - but for me, I had to eat a little more. I increased calories (but still under maintenance level!!!) and lost the last weight
I plateaued from March - June, I just kept at it. I kept telling myself, at least I am MAINTAINING which was a great feeling for me