by going into therapy what you say during the therapy sessions and any other conversations with that therapist is considered confidential files. The only time a therapist must disclose they are seeing you is if you are a threat to yourself or someone else to the point where hospitalization is needed.

A therapist must report threats of suicide
threats of harm that they feel is out of control
threats to harm another person (this includes if a client discloses they know of child abuse situations that are at the moment going on in the clients life or someone the client knows, or if the client discloses that they themself is abusing a child physically, mentally or sexually.)

If you go to a therapist and say I feel like killing myself that therapist will take time to find out how close the "I feel like" is changing to "I am going to"

If they feel the client is going to make an attempt they have to report it to their supervisor who will advise them of the agency protocal and that may include reporting to police for emergency inpatient protocal.

But just talking because you feel like you are going to explode and need a place to vent a therapist wont reviel who you are, why they are seeing you or even if they are seeing you.