(PW) unburden yourself, tell what’s bothering you
I feel better ever since I told him my problem and got it off my chest.
(free) get (something) off (one's) chest
To vent one's pent-up feelings.
(GoEnglish)
If you get something off your chest, you confess to something that has been troubling you.
(idiommeaning) (verb) to tell someone about your feelings or emotions, especially after not speaking for a long time
Mom: I need to get something off my chest. I hate your new boyfriend!
Daughter: But I love him!
A: Dad, I don’t want to study Law anymore. I want to be a dancer.
B: How long have you felt this way?
A: For 2 years. I’m only getting it off my chest now because I didn’t want to disappoint you.
B: You can never disappoint me, son!
Stuart’s roommate got something off his chest last night when he told Stuart that he was too messy.
(phrases.org)
The Oxford English Dictionary defines the phrase, "get something off one's chest," as meaning "to relieve one's mind by making a statement or confession," and cites as its earliest example "1902 Daily Chron. 27 Sept. 3/2 The desire is either to deliver a message to the world or to express the individual personality--to 'get it off your chest' is the horrid, vulgar phrase."
Although one need not concur in the characterization as a "horrid, vulgar phrase," it's true that it can refer either to something you feel you need to say because it needs saying, or to something you need to say because it has been "weighing on your conscience."
From the eighteenth century on, writers and especially poets have talked about duties, delays, other negative things as "weighing" upon people or their spirits. The case of the weight upon the chest is interesting, as references to body parts often have a physiological basis. Having "a lump in your throat" is an example on one which has been elucidated as a feeling which results from s specific chemical change in the body. Having something weighing on the chest almost invariably accompanies nightmares (although the converse is not necessarily true--nightmares do not always accur if something weighs on your chest).
