Could be several things. One thing is "hidden" carbs--review your food intake with a carb counter and make sure you're not overdoing it. About the only thing with truly zero carbs is meat & fat. And, water.
For example, most people don't count carbs in artificial sweeteners, but if you drink a lot of diet sodas or coffee & tea with sweetener, that can really add up. And, if you choose bad carbs instead of veggies, you probably need more fiber.
You also need to drink lots of water, might need supplements, and you could be exercising too hard. And, you need to eat frequently & not skip meals. When you stress your body with diet and exercise, sometimes it reacts by retaining everything.
And, you might just be eating too much. Low-carb is not about eating "all you want" of fatty meats or other low-carb foods. Go to Lisa's
Low Carb site & read her basics articles or buy the Atkins book or something so you really know how to eat low carb.
The big benefit is that it is so much better for your blood sugar, so you are less likely to binge on carbs. You can stay satisfied on reasonable amounts of good, lean protein and fresh veggies.
Good Luck!
