Please, please, please HELP ME!!! My bother in law just propositioned me!!?

I hate him!! But I am so afraid to tell anyone. If I call the police then everyone will know. My sister in law is the nicest person in the world and I would never do anything to hurt her but this would break her heart. And if my husband finds out he will KILL him. I mean he will REALLY kill him!!! What the heck do I do??? He keeps coming to my house when my husband isn't here and I don't let him in, but I am afraid he will come in anyway!! I keep the door locked, but he bangs on it like he is going to break it down!! I am really afraid!! He helped my husband get a really good job at the same place he works and now he says I owe him.