get sth off one's chest

off one's chest (out into the open)
get sth off one's chest (to relieve oneself of something that is emotionally distressing or stressful, usually by telling someone it; to tell a secret, talk about a subject that you’ve been thinking about a lot) — признаться в чем-л; снять с души камень (рассказав о чем-л. или признавшись в чем-л.); снять груз с души; обегчить душу

Example 1: There’s something I really need to get off my chest. It’s been weighing on me for so long. We can’t date—I’m married. (ebaby)

Example 2: Look, before we got any further, I have something I need to get off my chest. I used to be a woman.(ebaby)

Example 3: The fact that I had talked about Susan had been worrying me for so long that it felt great to get it off my chest.

see also
[make a clear breast of it]
[come clean]
[out of one's system]