Please do not worry!!

Nolan's head has always been off the charts, it scared me for the longest time. He is now 20 months and perfectly fine- with a big melon.

He also had flat spots (pretty severe) but once he started sitting up and being mobile, they rounded themselves out.
As long as they follow the curve (even if it is the high curve) that is a good sign.
Here he was at 4 months-
https://a1.sphotos.ak.fbcdn.net/hphotos-ak-ash4/33726_540150946602_59100351_31691873_8183968_n.jpg
And now-
https://sphotos.xx.fbcdn.net/hphotos-ash4/406825_596964731322_59100351_32185113_1327748159_n.jpg