my baby is premature (34weeks birth weight 1.8kg) now he is 3 months 15 days old (5 kg) but still he can't control his head properly, is this normal?

A. Your child is having a very healthy weight gain and the stability all of the head totally comes by the age of six months with a premature kid it could be 7 to 8 months also so right now the child is having a partial stable than that is good enough