Hi Heather --
I can totally understand your frustration - it seems to come off so much slower than it goes on, and it sounds like you're losing at a slower rate than fitday would tell you to expect.
We're about the same size, and I also use fitday to count calories, although so far I've found that I lose at about the rate it predicts.
Here are a few ideas for you . . .
Have you had a checkup recently? You might want to ask your doctor to check you for insulin resistance, and to check your thyroid -- either of these conditions can make it really hard to lose weight, and they are both treatable with medication.
If you don't measure your portions, you might try doing that for a week or two . . . I'm always surprised by how easy it is to underestimate portion size. I recently got an inexpensive digital kitchen scale with a tare feature, and I love it -- it makes it really easy to know/journal exactly how much I'm eating.
If you've been eating a very low-fat diet for a while, you might try incorporating more healthy fats (olive oil, salmon, nuts) . . . some believe that eating some fat can help stimulate your metabolism.
You might consider the type of carbs you're eating, as well as just the amount . . . if you're eating carbs with a high glycemic index, it may be the case that more whole-grains, vegetables, fruits, etc would help you maintain a level blood sugar, which might help your metabolism.
Some ideas for high-protein/low sodium snacks -- plain yogurt, low-sodium turkey breast, some meal-replacement bars (I imagine the atkins ones would be high-protein).
Good luck, and hang in there whatever your rate of loss may be . . . as long as that number keeps going down, you're making progress toward your goal.