Delayed walking

Hi everyone. if anyone can give any opinions or petua that would calm me down abit on this matter, my son is 20 months old and he is a 31 week premmie. he reached other milestones probably around a month or two late than normal babies. right now he can walk with support and stand up still without support. but he has not been walking independently and most of the time dia macam lazy nak cuba to walk.? but it upsets me when my in laws are always asking why he isnt walking yet and comparing with their other kids. i have so much sabar in me and i put alot of faith in him. he is a strong boy and i know he will walk one day.