Need advice

I am 24 years old and 5'6 and I weigh 165 pounds. I have been steady at this weight for about 3 years now and I just can't seem to lose weight. All I do is drink water. I have cut out all chocolate and high sugar foods. I have tried different diets and exercising. I need help. With my height I'm suppose to be around 125-135 pounds. I want to lose the weight before the summer.. my fiancé has lost 40 pounds in the last 4 months. We have ate everything the same and I have lost nothing. Idk what to do