“Sleep when the baby sleeps”

My baby is almost 4 weeks old and during the day I try to follow the advice of sleeping when the baby sleeps... however... he will not sleep in his basinet during the day! I rock him to sleep or he falls asleep after nursing and then I carefully place him in the basinet. Within minutes he is moving around and grunting and waking up. I’m so exhausted from being up through the night. I just wish I could get one little nap in! 🥴 He will only sleep in a boppy lounger or a little bouncy seat- both of which aren’t deemed safe for sleep so I only let him sleep in there if I’m awake and watching him closely. Any tips/tricks/advice!? Anyone in the same boat that I can commiserate with!?!