Personally - it sounds like he's just learning that there are things that go on when he goes to sleep... and he wants to be a part of it. If you give into it (and I did for my first) he'll most likely learn to cry until you pick him up and play with him all the time (as my oldest did). This is what I've learned to do - bedtime should be at the same general time each night if you can. Changing things up when needed isn't the end of the world or anything, but try to stick to a normal time/routine. All things you've heard before, I'm sure.

The thing is that when he wakes up I personally do go in to check on the baby - I just know that I can't let the baby cry and not
know that their OK, kwim? Once you've established that he's not hungry, needing a diaper change or in pain of some sort (babies do get their legs stuck between the crib slates sometimes...) then you lay him down just like before with a kiss and say a soft goodnight. And you walk away. The whole time keep it as dark and quiet as possible in the room and absolutely
no playing around. I know it's tempting, but playing in the middle of the night is a bad, bad idea unless you're fine with getting no sleep yourself.... for the next few months at least. It will probably take him a few nights of crying for what seems like eternity, but he'll get the idea and settle down to sleep. The longest I had one of my babies cry was 20minutes and I thought it was absolute torture!!! But then the next night she slept great and was quite the happy baby.

So stick with it and good luck!!
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