Sexual assault is a serious allegation. You should contact the police first. This is because sexual offences are criminal and only the police/state can initiate proceedings in criminal law. Then, you should contact a lawyer. You can contact your local community legal centre and the Women's Law Centre for some free advice and direction.
As for your counsellor, you could complain to the industry's professional body. Then, speak with a lawyer about possible offences they may have breached.