Have you ever heard of weight loss plateaux? This is such a common occurance! At the start of a diet you loose weight quickly and then the weight loss can stall or "Plateaux". This is a temporary thing and if you keep on with the diet you will eventually begin to loose weight again in a couple of weeks. You can stimulate weightloss by increasing exercise and temporarily cutting more calories for 1 week after you reach a stall or plateaux.
You say that you loose motivation after a few weeks. I think you might need help keeping your motivation up and sticking to your diet and exercise plan. Why not try weight watchers or similar group who can provide support and help keep your motivation up? ... View related article.
