I have a fear of getting fat?

Okay, So I'm currently 18 years old & im 118 pounds & stand at 5'1.. yes, I'm aware that I'm short:(! But anyways.. im content with my body, i have a cute butt flat stomach & im a C cup, and feel happy. I'm afraid that I'll get fat as I grow older!:( I rely on my body a lot, and I currently keep in shape by dancing. and If i ever do get fat I'd rather be dead. honestly. nothing against anyone. how do I prevent gaining weight:(