Oscar did the same thing hun. Plus he would only turn his head to one side it seemed.

I took him to a Chiro who specialises in babies and she did a few very soft minor adjustments to his back. She thinks it was out from the delivery

Give your MCHN a call hun... they're usually more than happy to help you over the phone. They can't advise you to take him to a Chiro or anything though... mine just said "Yes, it's something you could try".