Chances are extremely good that you aren't the only victim of your harasser. Speaking up can be helpful in finding support and in protecting others from being victims. Finding out who is responsible for dealing with harassment on your organization and whether you can talk in confidence to that person. Almost all organizations have sexual harassment policies, procedures and individuals or counselors who administer them. If you are a union member, speak to your union representative.
Unions are generally very committed to eliminating sexual harassment in the workplace.
If you are experiencing sever psychological distress, you may want to consult a psychologist or other mental health professional who understands the problems caused by sexual harassment.