Another prophet, Hananiah, shows up. He has a much sunnier message than Jeremiah, namely that god loves the Israelites again and is going to set them free and punish the Babylonians a full 68 years earlier than expected. Jeremiah is sarcastic in response.
Hananiah gets even more dramatic, breaking the yoke off Jeremiah and saying god is going to do the same to the people. God also escalates and says he'll replace the wooden yoke with an iron yoke. Before this can get into full-on Mutually Assured Destruction, though, god kills Hananiah.
Jeremiah writes a letter to the enslaved Israelites, who have been enslaved entirely on a whim from god for something a king did a long time ago, to suck it up, get married, have kids and grandkids, don't listen to false prophets, and in 70 years he'll give them back their country. He'll also repeat all that vile shit he did to them, only the Babylonians will be on the receiving end this time. The false prophets and their children will be burned, exiled or relegated to the stocks.
The men are all walking around with their hands on their thighs like women in labour. Apparently Jeremiah has never seen a woman in labour. Also, if men had to give birth it would be awesome. The entire rest of the chapter is a riff on the theme of 'god will restore his covenant with you and punish his enemies.'