Losing Weight is a not a linear process, and it is quite unpredictable.

Losing weight is usually not linear.  It is more of a curve than a linear one.  It might start off quite rapid but it slows more and more as you near your goal.  In most, there are setbacks from time to time that can be quite discouraging.  Some days you may lose weight, and during others, you may gain a little.  You should not be discouraged by these small roadblocks and instead, keep focusing on the goal.  It is normal for your body weight to fluctuate by a few pounds when your hydration or salt intake changes.  

The bottom line: You need to focus on your goals.  Losing weight can take a long time and many small blips along the way.  The process is not linear.  In fact, I would say that the process is more like a parabola in which your weight tends to fluctuate up and down by a few pounds and does not maintain a line or curve.