I can't say for certain because I don't know your lifestyle, body shape, exercise history, food intake etc etc, but here are some possibilities:
I am NOT taking into account breast feeding as I don't know much about that time of life and weight loss, but this is what I get my clients to do
1. Change your diet - calories aren't the be all and end all of weight loss. You need to look at your macros (carbs, protein and fat). On average, you should be eating:
- Protein: your weight in kg multiplied by 0.7 to 1.0 - this is your protein intake in grams. Multiple by 4 to get the calorie value
- Fat: 20-25% of your total calories as healthy fats (divide by 9 for grams)
- Carbs: your remaining calories (divide by 4 for grams)
Aim to eat the majority of your carbs during the first half of the day and severely reduce this towards the end of the day. However, if you are exercising at night, have a protein based snack with carbs afterwards e.g. A protein shake with a banana.
2. Change your exercise - the majority of women believe cardio is the only way to lose weight
STOP.
Weight training is the way to go, and I'm not meaning pissy weak little weights, I'm talking about ones that challenge you. You should begin with an aim of 2 sets of 12 repetitions for 3-4 weeks, then up the weights and lower the reps to 2-3 sets of 6-10 reps. See a trainer for a program that is catering specifically to you and takes into account any medical/physical issues that may complicate exercise.
Now, I don't mean do no cardio at all, just cut it down. Unless you're training for a long distance event, 20 minutes of high intensity work or 30-40 minutes of moderate work is enough a few times per week. Add in 3 sessions of weight training and you'll boost your metabolism and turn your body into a fat fighting machine.
3. Take a break from the 'diet' - sometimes the body just needs a bit of a shock to get the system working again. If you've been on a healthy calorie controlled diet for a while now, add in a cheat meal/day. This means that you may have something that is less healthy for you without the binge. Personally, every Friday night, I go out for dinner and order what ever I like. I still avoid foods that make me bloat and feel sick, but I don't worry about the size of the meal or what is in it.
4. Don't weigh yourself - at my (measured) biggest, I was 76kg with 33% body fat (25kg of my weight was fat). When I got into the fitness industry, I only lost 2kg and was so disappointed at all my efforts, however, I had lost 8cm off my tummy, 10cm off my hips and 3cm off each of my thighs. Took my body fat and I was sitting at 28% meaning I had lost 5kg of fat and put on 3kg of muscle. Weight is not a perfect indication of health. You are better to measure circumferences than weight as muscle takes up less room - so you could be the same weight, but a dress size or more smaller.
Hope this helps. It will take a while to change your way of thinking, but once you do, the results start to speak for themselves
EDIT: I forgot to add that you should eat 5-6 meals per day (meals, not meals plus snacks) spread out about 2.5-3 hours apart. Also, when exercising, eat 1.5 hours prior and then a protein based meal/snack (i.e. protein shake/bar/chicken and rice) within 30 minutes of finishing exercise.