Have you talked to your doctor about this? I have no idea when you're supposed to start dropping the pregnancy weight, so could this be within normal parameters for post-pregnancy weight loss?
Could you be buildling muscle through your added exercise, or retaining fluid because of heat? If you track your measurements as well as your weight you might see some discrepancy. If you're building muscle then the scales could stay the same while your actual size decreases.
Another possibility is that your body has adjusted to low-carb so well it's hard for you to lose weight on it. Could you try a different plan for a while like low GI or calorie counting? Someties shaking your body out of its routine is enough to start losing weight again.
It might be worth going to Calorie King (http://www.calorieking.com.au
) and creating a profile to see how many calories per day you should be eating to lose weight. Then just type in what you eat and how much of it you're eating and see what the calorie total comes to. While it doesn't sound like you're having too many calories there's a possibility you're having too few. If you're eating too little then your body may have gone into starvation mode, where your metabolism slows in order to protect you from famine conditions.
If you think it's a matter of being on a plateau Spark People have a good article about this: Plateau Busters