I plan on leaving Home How do i explain myself?

Hey i'm currently 17 Turning 18 i have a boyfriend thats 18 already who moved and now lives in Virgina i want To move Out There With him when i turn 18 But how do i Explain To my family that i'm moving to Start a life in Viringa and start going to college there when i live in New York especially if my family tends to treat me like i'm still a little girl i dont want to just leave because i dont want them to worry please help me :-(