Head Circumference small??

So I’m about to be 33 weeks and baby is measuring as a whole in the 67th percentile! But her head circumference is in the 4th percentile now. It’s only measuring a week behind from how far along I am and the doctor and nurses said it’s probably just genetic it’s not a big deal. Everything else is measuring perfect. But it’s still uneasy for me. They keep reassuring me it’s nothing but it’s worrying me!! Any stories about this?? Of course Dr. Google has freaked me out and now I’m convinced she has microcephaly 😵‍💫