I almost always feel better after having told my therapist about something that I feel ashamed about. (Usually it feels God-awful in the moment, and then I feel some relief afterwards. Sometimes the relief is accompanied by an enhanced feeling of closeness with the therapist, which often feels nice to me.) I think it's one of those "act as if you don't feel ashamed and then you won't feel ashamed"/keeping the secret is worse than just talking about it things.

That being said, I have friends who have experienced serious traumas and for some of them, talking about any aspect of trauma in anything but the safest and most controlled circumstances can lead to dysregulation.