“Woe is me, my mother.” The speaker now shifts to Jeremiah. It had been God. The reader is expected to notice the shift from the content itself, the Bible does not point out the shift. Jeremiah is under such pressure that here he laments his birth, similar to Job (cp. Job 3:1-16). Jeremiah was called by God from the womb, now things are so difficult in his life that he says he regrets being born. It is doubtful that he actually did, but his grief was deep and he expressed it by saying he wishes he had not been born.
“a man of accusation and a man of contention.” The two Hebrew words, rib (#07379 רִב), here translated “accusation,” and madon (#04066 מָדוֹן), here translated “contention,” were used in the legal system, and used of accusations and legal cases and also of the contention that occurs in courts. The genitive construction, “a man of accusation” can have either a subjective or objective meaning; so it can mean that Jeremiah instigated the court cases and contention, i.e., he accused others, or he was accused and contended with by others. Also, however, the genitive case leaves open both possibilities; sometimes Jeremiah accused others and sometimes they accused him, and that is likely what happened. Here in Jeremiah 15:10, Jeremiah expressed that he felt like he was always in battles with people and it was difficult for him. Frankly, he likely was in almost daily battles over the Law and doing what was godly, and that would have been difficult, but that was the ministry that God called him to (Jer. 1:10): that was what God wanted and needed him to do to try to call godless Judah back to God.
God called Jeremiah to an extremely difficult ministry, and although Jeremiah was up to the task, it did not mean that he did not often personally suffer for it. The fact is that the world is very ungodly, and people who stand up for God and take a stand against ungodliness regularly suffer for it. That is why we must know that great rewards will be given to those who stand for God and we must draw strength from that hope (Matt. 5:10-12). Even Jesus drew strength to endure the cross from the joy he saw coming in the future (Heb. 12:2), and we must also draw strength from the hope that is promised to us (Rom. 8:18).
“I have not lent.” In the context of breaking (or “stretching”) the law, “lending” was lending with interest (cp. Deut. 23:19).