My LO is 7 weeks old and for naps and bedtime, I'll swaddle and put him down on his back. I will always rotate him in his crib and have even placed a rolled up blanket behind him to tilt him slightly on his side. nevertheless, my LO's head is a bit flatter on his left side. He can't roll over yet and my mom's advice is to have him sleep on his stomach. He is pretty good with tummy time but I'm still hesitant to have him sleep on his stomach. Any advice?