ANDY'S ANSWER: There is no way you are going to stop your brother from teasing you about something he knows bugs or embarrasses you. I would suggest you take some steps to deflect him to other things. One way would be to start writing things in your diary that are complete works of fiction. Like you overheard your parents saying they were going to buy you a new car when you got your license. Or you wrote to (celebrity of your choice) and they had written back that you were the kind of girl they were looking for and wanted you to come to LA to meet them, etc, etc.