Try to carry baby more often and don't let him lie on his back too much if that part is flat try to put him on the other side, my LO last time head flat as he has bad acid reflux so always lie down on his back now I put him sleep on his side and change his position every now and then it grew back
How young po? Does your little one have that already upon giving birth? If not try massaging the head roundways frequently and use pillows that has something like a hole in the middle..
Make your LO sleep on his/her side and change sides frequently. I never let my kids sleeps on their back when they were baby (swaddled) until about 3 mths.
My pd said no need physiotherapy no need helmet. Not sure if he’s too relaxed. My baby head is flat on the side he always sleep on