Diet, nutrition, weight gain and loss are very complicated issue. If you have never done any research, on this subject this might be a good time to start. It will help you understand how it works and not feel so frustrated. Assess your way of eating, your allotted calories and your elimination pattern. Remember, you have 26 feet of bowel full of s**t and if you are not eliminating effectively your weight will go up. Walking is great exercise, keep it up but also consider swimming, aerobic exercise classes. And resistance training. Don’t get discouraged. Learn and just keep going. Persistence pays off