Sleep tips (nap time)

Has anyone got any tips when it comes to naps? He’s 14 +4 weeks and he’s been napping on us since about 7/8 weeks. I have tried so many times to get him to sleep in his next to me but simply refuses or wakes up 5 minutes later. The most I’ve managed to get is 40 minutes. I’ve tried putting him down sleepy but awake, he just lays there and smiles at me after rubbing his eyes and drifting off on me. I’ve tried putting him down different times after he’s asleep in my arms but he either wakes up during the transfer or moments after 😅 I know he’s still little but I feel like I can’t do anything unless my husband is around to take him. He does fall asleep in a carrier but little man is getting to be a chunk and I haven’t got the greatest back (feels even worse after my c-section) and I’m just wondering if anyone has any magic tips. He sleeps in our room with the blinds shut to try and darken the room. I have one blackout curtain but we have 2 windows so I don’t think it’ll make it much darker. I don’t have any white noise machines simply because I tried this using my phone and it made no difference for us. I have the grow egg in the room emitting yellow/red light with the heater on to make it 20 degrees. I track his wake windows just to see how he’s doing and to avoid over tiredness along with watching for sleep cues (he rubs his eyes and his eyebrows/eyes start to get red) He’s also exclusively formula fed (he drinks 8oz every 4 hours 4 times a day if that makes any difference) I can put him to sleep on me within seconds, just not in his bed 😭