I don't think you need to drop your calories that low. I weigh 166 now and I lose 1-2 pounds a week eating about 1300 calories. Since your weight is higher, you'll burn more calories a day.
Since you are already counting calories, try signing up for a site like FitDay.com or LifeStrong.com. They can help you calculate your calorie needs for weight loss. Eating too low can actually slow your weight loss and you should not eat under 1200 calories a day, no matter what. Having a low day once in a while is fine, but as a general rule, stay over 1200.
Also, are you exercising at all? That can help burn more calories and you'll maintain your lean muscle, so what you lose is fat. You'll also be able to eat a little more if you are active.
And, you can't expect to lose 3 pounds a week every time. A good rule of thumb is to aim for 1% of your body weight a week. So, for you that would be about 2.4 pounds a week, but as you go down, the weight loss will slow. And you'll have weeks where you do everything right and don't lose an ounce, it's normal.
That said, 5 days really isn't much. Try to weigh yourself just once a week if the scale is driving you crazy. I doubt this is a plateau, since you just started, but you should know that they are normal and can last a month or two. Also, be sure to drink a LOT of water. Water retention could be the reason you are going up and down.