What Exactly Had Happened?

Class going to start next week. So, the holiday is almost over. I've been spending my holiday by staying at my room and sleep almost all the time *hibernating mode*. But there's a weird thing happened yesterday. As you know, I'm living in this house with my bro and the other people. I'm the only girl & considering that fact, I've always take a safety precaution especially, always lock the door. When I woke up at yesterday, I noticed that my door is opened. Not widely open, but it's opened. I'm seriously scared, confused and thinking hard. What I can remember, before I go to bed, I did checked & lock the door. I don't know how did it happen. Is it my bro who forgot to close the door? or is it me, who open it by myself during sleep? or is it other people who open it? I hope not. I'm scared to ask my bro. I hate myself for sleeping like there's no tomorrow until I didn't realize I'm sleeping with the opened door. I should be careful next time.