“you have broken.” Although the Masoretic Hebrew text is pointed to read “I have broken,” the Septuagint and Vulgate read “you” which fits the context better, and Keil and Delitzsch refer to this as an Aramaism and give grammatical and contextual reasons why “you” is correct (Keil & Delitzsch Commentary on the Old Testament). Here Israel is compared to an ox or donkey that has rebelled against its owner, broken its bonds, and ran off to do whatever it wanted.
“spread yourself.” The definition “spread” is given in some Hebrew and Aramaic lexicons (cp. HALOT and Holladay). The Brown-Driver-Briggs lexicon was more opaque, only daring to use the Latin: in sensu obscoeno (in an obscene sense). God is being very graphic and not pulling any punches in letting the people of Judah know exactly how he felt about their idolatry. Judah was in a marriage covenant with God, but she was spreading herself spiritually by committing adultery with other gods, and physically because the people were involved in the ritual sex connected with the worship of those gods.
“prostituting yourself..” Ritual sex was often part of the worship of pagan gods. The people of Israel committed spiritual adultery and physical adultery right along with it.