Congrats on the great progress you have made - you deserve a big ole pat on the back.
As Michael noted, plateaus happen. I totally agree with his suggestions.
One thing that helped me, and others, is to take a break in the low calorie regime, and try to eat the amount of calories recommended for maintenance at your current weight for a week or 2. Then return to the low-cal routine. Sometimes our bodies just need time to adjust to our new size. This was recommended by my diet doc a couple of years ago and while it can require a little discipline to get back on the lower calorie program after eating normally for a while, it seemed to work for me.
2.5 years, 45 pounds later... 128ish pounds