If this is the case for you, then there is much to be fixed hormonal, metabolic and behavioral. Find a professional who can help is an important first step, but in the meantime I recommend you take a copy of the last book, which describes how a metabolic makeover better than anything I've read.
All that said, losing a few pounds for the second time, it's frustrating, annoying, and a waste of your time. To avoid again, follow these tips:
1. Know that you can not return to "normal diet". Normal diet had problems first. You do not need to diet all your life, but you can not go back on his past relationship with food.
2. Uniform application is your asset. We all have a way of thinking that we are more in agreement with our food than we really are. You must follow the diet with an application, a spreadsheet or pencil and paper to keep you honest and do for the rest of his life.
3. Despite daily. Although the scale is a terrible measure of progress of weight loss in the short term, is a beautiful and simple marker long term. No pay close attention to changes in day to day, but keep the number so you can identify long-term trends of weight changes. See you when I only gained five pounds is a lot better than "suddenly" realize that you are 15 pounds heavier.