Baby won't go back to sleep

My baby is 8 weeks and until several days ago, he would wake up in the middle of the night, I'd breastfeed him and he'd fall asleep. After a few minutes I could put him back in his pack n play and he'd be fine. Now he is suddenly really hard to get back to sleep. He takes longer to fall asleep and is sometimes fussy before falling asleep. And when I go to put him down he usually wakes up. Anyone else had this problem? I've started reading about wonder weeks a little, could this be part of the 2nd leap?