my 6 week old girl is possetting after feeds,al...

my 6 week old girl is possetting after feeds,although i know this is normal ,but was wondering if she may benefit from a different formula. She is currently on the Nestle Nan Gold Formula.. As of late, she is unsettled when its time to sleep and only seems comfortable and settled when we allow her to lay on her tummy on our chest...i am not sure whether this is for pure comfort and has us worked out or whether she is in some sort of pain with reflux??? she does not scream of lift her legs up as i have been told that they are the signs , but she does grizzle when we try and put her down on her back in the bassinette....