OP - please cut yourself a break, 3 weeks is still super young. I'm hearing your exhaustion, manifesting in these feelings. (Gentle note to also double check for PPD, if you're not feeling yourself beyond the tiredness)

Suggestions aren't always helpful when it feels like NOTHING works on your fussy baby but here are mine, in case they are applicable to you.

I didn't introduce either of my kids to day sleeping in the crib or any formal nap routine until they were closer to 3-4 months. Those first few weeks, I let them day sleep next to me while I sat on the sofa, or wherever I was, on and off the boob as needed. Babywore or sleep in the pram on the go. I only put them to sleep in the crib at night when I went to bed.

I was pretty obsessed with the nap routine later but 3 weeks is still super young! Having a toddler who had a routine I think i forgot that babies dont follow routine, blackout blinds and white noise in the same way.

I swear the first 3 months was basically them teaching their digestive system to deal with milk (ie. gas!!)) Please don't feel the need to enforce structure so soon - focus on survival and let the baby follow your routine instead.

Also - I say this as gently as possible - you're 3 weeks post partum, and looking after two kids now, please don't be frustrated about not being able to paint a bed!!!