Flat head on 3 week old

So my 3 week old is showing a bit of flat head, I got him one of those pillows but recently he was having issues with gas and constipation. I noticed he slept better without a pillow. That is when I’m noticing his head now. We are Asian and having a round head is something in our culture everyone notices. My mom is currently with me and keeps pointing it out. Any tips how to fix it? I really hope I don’t have to make him wear the helmet he’s still developing so I hope it will get fixed on its own.