Can I be farther than what they say?

My fundal height on Dec 12 measured 29 weeks then I went again in Dec 21 I measured 31 weeks. I told them the wrong period date but my baby is due Feb 18 by an ultrasound. I’ve been dropping for 5weeks now and I feel her head moving from side to side in my pelvic. This is my first time being pregnant. Could I be farther than what they say???