Hoping to get hive wisdom on what is going on with our 21 week old. He's been sleep trained to fall asleep on his own since 3 months, and we nap trained last month. He's STTN a number of times, but typically has one wake up a night to nurse. I'm fine continuing to nurse him once a night but two issues have suddenly developed in the past week.

First, he randomly wakes up very upset between 10 and 12 (asleep around 6:30). Second, he used to just nurse back down to sleep and I'd put him back in his crib. Now when I put him down he cries hard for at least 10-15 minutes. I've tried picking him back up to nurse longer, but after 2-3 attempts just let him cry. I don't understand what's going on, so I don't have any strategy here.

Is this the 4 month sleep regression coming a little late? He's is teething but has been for weeks, with no visible change lately. Is it time to night wean? I'm not against using CIO but I only want to let him cry if there is an actual purpose and it is temporary. Has anyone gone through something similar? Help!