Jamieson, Fausset and Brown on Jeremiah 45:3

3. Thou didst say, &c.--Jeremiah does not spare his disciple, but unveils his fault, namely, fear for his life by reason of the suspicions which he incurred in the eyes of his countrymen (compare Jr 36:17), as if he was in sympathy with the Chaldeans (Jr 43:3), and instigator of Jeremiah; also ingratitude in speaking of his "grief," &c., whereas he ought to deem himself highly blessed in being employed by God to record Jeremiah's prophecies.

added--rescued from the peril of my first writing (Jr 36:26). I am again involved in a similar peril. He upbraids God as dealing harshly with him.

I fainted--rather, "I am weary."

no rest--no quiet resting-place.