I need to tell you that I am partial to Jeremiah as a servant of God. He lived in what many considered the golden age of Josiah where Israel's influence and peace and safety were unparalleled. But then with the fall of Josiah so came the fall of Israel, and it came hard, and Jeremiah was there for that as well. He experienced his people deported into captivity in Babylon. So as a prophet he was able to experience the super highs of ministry with a successful king and a God who seemed to be listening and responding and blessing, as well as being on the end of a silence that was deafening. This is where we pick up in chapter 1 as king Josiah reigns and begins his reforms which were based upon the discovery of the Word of God.
The first chapter is pretty much a timeline which gives us the dates that we need to understand when the ministry of Jeremiah took place. He served under Josiah who was king from 640-609BC, then under Shallum who only served for one year in 609, then for Jehoiakim who served from 608-598, and then for Jehoiachin who served in 597 and Jerusalem was sieged that year by Babylon. He then served under Zedekiah from 597-586 which is when Jerusalem actually fell and the people were sent packing to Babylon.
I don't know where you stand on the topic of abortion but I have always seen vs.5 as an indication for me of the potential that people have which is in them even before they are born. This verse is used universal by the camp which is opposed to abortion to make the case that the unborn life has potential and it is a potential which is instilled by God. This is true also from a reformed perspective where we believe that God has called all people to be God's people and than even from before we were born and able to respond to God, God chose us as His children.
Jeremiah objects to God calling him to serve him because he self identifies as a "boy". The call to Jeremiah is found in vs.5 where he is to be a "prophet to the nations". God touches his mouth and as a result gives him the words that he is to speak. That should sound a bit like the calling of Isaiah, except Isaiah had a burning coal put to his mouth in order to cleanse him for the ministry.
But like Isaiah, he gives Jeremiah a message that would probably want him to say: How long!? God tells him to gird up his loins and stand tall and do not break down before them, or else I will break you personally. Go get em champ! What we will see is that the messages that Jeremiah is told to pronounce are very, very difficult messages for the people of Israel to hear and will only promote anger in the people against the messenger. This is one of the reasons why Jeremiah is called the weeping prophet.