I started a routine at 5 weeks with DS because I was developing PND and needed structure and some time to myself to get it all together, a lot of people said it was far too soon and it would never work but much to my amazement I found it worked from the afternoon I started!
Maybe DS is a naturally good sleeper or it’s a fluke and I’m in for hell soon but it’s got me to 15 weeks with a few hiccups here and there but nothing awful
Here’s what I did:
Bought and read 7am to 7pm sleeping baby routine by Charmian Mead after some good reviews online. It changed everything!
DS is also FF and this book works well for that
I didn’t follow it to the letter (for example, we use HiPP Organic milk which DS loves but she doesn’t recommend and DS has a dummy & is in our room which she also doesn’t recommend — BUT the general routine works perfectly for him!)
I found the stuff about ‘awake times’ and food really helpful and the routine also helps me figure out the reasons he might be crying - the hours of this used to cause me a huge amount of stress
I also found the little ones 3-12m routine answered a lot of the questions I had once we got to that stage that the book stopped covering
DS now has 3 naps a day (45m in the morning, 2hrs in the afternoon and 15-30m in the afternoon) and sleeps 7-7 with the odd grumble here and there but nothing awful. He dropped all night feeds at 6 or 7 weeks of his own accord and is a very happy baby that grows like a weed so it’s working for us
HTH, happy to answer any q’s if you have them