MY SISTER READ MY PRIVATE MESSAGES...! 10 POINTS.?

[We can go nowhere but up]

Okay I know i'm young but what's done is done so please don't preach to me thanks.
Okay since I don't have a phone me and this guy i have talked to for awhile message on facebook. Well ever since we started talking again my sister has been wanting to read our messages together I know she has. So I would delete them ( we have eachothers facebook information just because we are really close and we NEVER USUALLY SNOOP) and if he did send me a message the read message thing would show up and she couldn't check it then... Well she went over her friends' house and I stayed here. Let me explain to you the messages are really bad. It's about fooling around with him, and what I have done and what he wants me to do to him and what he's gonna do to me..... and I was wondering why he didn't answer me then I realized he has answered me but the red message reminder wasn't there and it seemed somebody CHECKED my notification for it. SHE'S THE ONLY ONE WHO KNOWS MY PASSWORD. and so I just know it's her. she hasn't come home from her friends house but I find it extremely hard to ask her about it. Idk if she is gonna ask me about it but that was private and I really don't know why she read it. I DON'T READ HER PRIVATE MESSAGES BETWEEN HER AND HER GUYS SHE TALKS TO. only when i was about 10 but that was 6 years ago. She is 22 and i am 16. I don't want her to think I am a slut. But she probably does. We come from a family where my mother EXPECTS US NOT TO DO THAT. and we all are suppose to lose our virginity around 20's and not do any of that stuff with boys until we are 20 ....( idk my mom thinks she controls everything)... so Idk . we are really close. but when it comes to that stuff I already told her I'm a very private person and don't like people knowing anything. and i know she thought i wasn't like that so im very ashamed ... btw it explained that I was gonna give him oral sex... and that he would do the same to me... yes im young but I really like him so please don't preach. what should I do?
I did change it,