'Self sooth' is nonsense. Only being 3 weeks old, I personally wouldn't feel comfortable leaving my child in a room on her own, I waited to put mine in her own room for months. got her used to sleeping in her Moses basket (not a crib, 3 weeks is way too young to be in a crib).
Your child is seeking attention, if you leave her to 'self sooth' it's just going to make the situation worse.
It will take some time to get her used to the room, so first make sure there are no distractions in there that will prevent her from sleeping. Dark room, very dim night light (bright night lights are the worst).
Stay in the room when she sleeps, wait until she is asleep and then wait a little longer. My daughter would always wake up after a few minutes, don't be in a rush to get out of the room once she's fallen asleep, this will give her confidence that her parents are there and haven't just left her in the room. wait 5 or 10 minutes after she has fallen asleep before you leave the room.
· 1 month ago