What i was told by my husband's grandmother is that you must keep changing ur daughter head position as in dont keep staying at 1 position
On my experience with my lo, it was still flat up until 6th month. It will return to it's "normal" shape eventually.
If you are worried, can request to see the doc when you bring baby for vaccination. Can ask the doc to help assess
Maybe you try using baby safe pillow. I use for mine when she was 2mths now 4mths, can see the difference