I really want more privacy?!?

[bunbun]

Im a 14 year old girl sharing a room with my 19 year old brother. I always respect his privacy, plus whenever he needs the room, he has the ability to use it anytime. He can get changed for work and not worry about me cause im always at school. Yet, he saw me butt naked 3 times cause he cant even knock before coming in even when I told him I was changing. Im sick of this shit. Im a girl i want my own goddamn privacy. Right now he has been sitting near my bed just "chilling" and its really annoying caue I sleep naked lol but for certain reasons. What should I do? I want him to give me more privacy.