If you are the victim of extortion, you should go to the authorities, like the police or the prossecutor's office and make a complaint and have them investigate your claim. Beforehand, it would be a good idea to have a conversation with the person or persons who are extorting you and tape record the conversation of which you are a part. It will help prove you have been extorted and protect you from being accused of making a false claim.
Always keep a copy of any tape you make outside of your home/apt. so you have proof if it somehow later disappears after you've given it to the police or DA.