My LO always has a rough time after shots, always throws her through a loop for a couple days, But I would guess that what you are experiencing may be related to the growth spurt they experience at this age.
Around 6 weeks, I remember my LO being really fussy, and usually it was late evening, at that point (maybe just a little earlier), we couldn't get her settled down for night sleep until at least 11 or 12. Rest assured it gets easier.