Ellie--You may be at a plateau. And if you've had the weight on for more than a year or two, your body is going to really fight you on allowing it to go. I'll share a quickie with you that is only meant to break a plateau and be used for 3 days only... and never more than once every 4-6 weeks. It works splendidly for me, and I've kept the weight off for almost 2 years now.
Before I proceed, just checking to see if your water intake is sufficient? No matter how bad I blow my eating habits, if I'm drinking enough (and I drink 10 8-oz glasses of water every day), I can minimize the damage. Also, get yourself some protein bars--I buy Pria because the calorie count is lower and I don't need a big honking bar to satisfy me. Shop around if you don't like those flavors, but try to stay under 180 calories if you can.
Morning: 2 eggs, 1/2 orange
Lunch: 4-5 oz chicken or turkey breast or white fish, 2 cups green leaf lettuce with cider vinegar dressing (I've learned to love this.. the oil only allows it to stick to the lettuce, and I dip it with gusto)
PM snack: 1/2 orange and protein bar
Dinner: 6 oz lean protein (see above), 2 cups green leaf lettuce with vinegar
Give it a shot for 2-3 days, and you'll see if you were at a plateau. I used to dread doing this, but I like it now. I feel so much better afterward. Oh, and NO salt. You can use Morton Lite Salt sparingly (it's got more potassium than sodium). And NO brown sodas, because the coloring contains sodium. Diet and clear if you're going to do that, but I don't recommend it unless you've reached your water goals for the day (that is my cardinal rule now).
I hope this helps. I can get 2-3 lbs off by doing this when I do. I might just do this myself over the weekend.
Betsey
"There are only 2 ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle."
Betsey 
