Night weaning help!!!!!

I’m trying to wean my Co-sleeping 21 month old from waking in the night for milk cuz he does it a couple times and I know it’s out of habit. I started Sunday night and it’s been sooo rough already... he wakes up at 3:00 am and stays up for 2 hours fussing and crying. He did it again last night and I’m soooo dead tired at work. I don’t even know how I’m at work on time this morning.

I was trying to work in stages 1. Night wean 2. Sleep in own bed.

Should I do it all at once?

I thought now would be an okay time cuz he’s not teething and not sick anymore...

PLEASE HELP!

Any advice?

Does it really take 21 days to break this habit?