K.L.
If you can give him more tummy time during the day it helps. Spread out a blanket on the floor, or play pen and let him play on his tummy for an hour or so a couple times a day. Also use bouncy seats where he sits up without resting on the back of his head. Activity centers are great to sit in and explore all the gadgets on the tray. Sit him in a Bumbo seat on the floor for a while too. Any position that keeps him from laying on his back will help shape the head right. Also it wont be long and he will be turning over in his crib and you wont be able to stop him, and the head will shape up nicely.