You seem to actually be at a decent calorie level for your current weight...if you didn't lose for two weeks, lost 6 pounds the next week, and then didn't lose anything the third week-when you average that out, you actually have lost an average of 1 1/2 pounds per week during that time.
What seems to be happening to you, is what happens to ME. I don't lose 1-2 pounds a week, every single week, like clockwork. It just doesn't happen. I may not lose for 2 weeks...then I can drop 3-4 pounds...then I don't lose for a week, then I drop a pound...and so on and so forth. The human body doesn't lose weight in an exact amount-even if we are counting calories, and counting the calories in our workouts like clockwork.
If you want quicker results-then intensify your workouts a little...maybe a slight drop in calorie level-say, 1900 a day rather than 2000. (You don't want to drop 200-300 a day at one time-it will make it harder to lose later on when you are smaller, and don't really have as much room to drop it in.)
I would not say that you are in any sort of a plateau at all, though-because over the past 4 weeks you have lost 6 pounds-it just hasn't been "evenly" 1 1/2 pounds per week over that period of time.
You are doing great. Keep it up.
Aphil