Go to the police right away. This man is threatening you and you won't be the last person he threatens. He is unstable enough to believe that you would reunite with him after blackmailing you. That is a very twisted mind and you need help managing him. If he is determined to Publish the pictures, it is going to happen if you do not act. By identifying him to the police, he will be aware that they know he is the source of the photos. You will also have him frightened to do anything else to you because the police will suspect him first.