You've just entered the weight loss plateau zone. Where did you go wrong?
First off, it's not your fault. The weight loss plateau is just a part of every low calorie diet. It's your body's natural response to famine. Low calorie diets scare your body into thinking food is scarce, and it holds on to what you've already got as a reaction. In fact, sometimes the body will actually store more fat for reserves, in case the famine gets worse. Not a good thing to have happen when you're trying to lose weight!
When you go on a low calorie diet, some of the pounds you lose are coming from muscle. Your body doesn't lose much real mass healthily this way, even though it seems nice at first. While some of us do retain more water than we need, it's important to keep in mind that we're supposed to be made up of mostly water. After all, lean muscle tissue is about 75% H2O! And speaking of lean muscle tissue...
Your metabolism depends in large part on how much lean muscle mass you have. Since low calorie diets usually involve the loss of muscle mass, they slow down the metabolism as well. In turn, you don't burn calories as quickly. And since burning calories is what this is all about, you may feel like you're shooting yourself in the foot.
That's exactly what you're doing, if you go on a low calorie diet. Not only that, but you're making things hard on yourself by staying tired and hungry all the time. (You're probably making things hard on your family and friends, too--have they said anything about the mood you're in yet?)
How do you climb down from the weight-loss plateau? It's pretty simple, really. Get off the low calorie diet! There are diets out there that don't make you starve on famine portions of food in order to lose weight. So do yourself a favor and stop torturing yourself, and find a new diet!