How can i gain weight and stay in shape?

[LaraineThomas]

I weigh 122 lbs and I'm 5"6. Idk how its happening but I keep losing weight along with my boobs and butt. I eat everyday. How can I gain my weight back and still stay in shape? I want ma stomach to stay flat but I don't wanna become anorexic. I don't wanna take any gain weight pills either.want everything natural.