Actually 5 pounds a month is a little over a pound per week, which is a
fantastic! 1-2 pounds per week is recommended, so you are right in the recommended range. Don't be misled by those shows that feature people losing ridiculous amounts of weight per week; that isn't realistic unless you are in some kind of special program with a doctor's supervision, a personal trainer, and a nutitritionist, and several hours a day to focus on losing weight. I started at about your starting weight and the most I ever lost in a month was five pounds (and towards the end there were a lot of months where I lost less than five pounds, sometimes a lot less). So you probably shouldn't expect to lose weight much faster than this.
The 3 pound gain in week 3 was probably just water, esp. since you lost it quickly the following week. (This does illustrate why its good to take your measurements once a month so you have another way to measure your progress besides the fickle scale).
Congratulations! You are doing great!