Small belly on 6th month pregnancy

Hi mommies! Ask ko lang kung normal lang ba na maliit pa ang tyan on 28th week pregnancy. 1st time ko po magbuntis and sabi ng lahat ang liit daw ng tyan ko, parang busog lang daw. I'm 4'11 in height and 97lbs. Does this mean unhealthy kami ni baby? Any advice po. Thanks!