Hi My 2 Month Old Son Is Having A Flat

Hi my 2 month old son is having a flat head on the left side. He always sleep on left and we tried to make him sleep on his right but since he feel comfortable at his left so always turn his head on left. laying down on his left has caused his left side to go flat.
I have heard that some kind baby helmet can restructure the baby head since baby is in his early state and still growing we do have a chance to make it right.
Any solution to this problem