Don't be discouraged. Good job on the walking! But be careful using the scale as a guide to your progress. Your body measurements will be a much better indicator. So many factors go into your weight: time of day, fluid retention, clothes you're wearing, etc...
If you must use a scale, be sure to weigh yourself once a week, on the same day, same scale, same time of day, and under the same conditions.
For instance.. I weigh on Monday morning, first thing after going to the bathroom, completely naked, and on the same scale every time.
But I think the best thing is to just discard the scale altogether.. get a nice measuring tape.