My LO was doing the same thing and I discovered I have too forceful of letdown and my LO was not getting enough of the hind milk (the fattier, keeps them full longer milk) I've only started this yesterday but it was a success, he slept peacefully for three hours. I feed him just on the left breast before bed, two feelings. This helped him get to the hind milk. When he woke at 3am, I fed him on the right breast, I could tell he didn't get much hind milk and he was super fussy, waking up after an hour. I feed him on right again and I think he got more hind milk as he's still sleeping peacefully and it's been 2.5 hours.