Won’t sleep in crib. HELPPP

As soon as I set my son in his crib he instantly wakes up. I’ve put blankets in the bottons of my crib and that’s the only way he will sleep in it but I’m scared of him suffocating. He’s 4 months old. He does fine with sleeping in my bed by himself. Any tips of how to make the crib more comfortable to sleep in? He hates the hard crib. He’s way to big for his bassist. He has been since a month old. 😩 since he rolls but he’s almost 20 pounds.