My daughter is 3 months old. Now 14 weeks .  She was a preterm baby (36 weeker ) with birth weight of 1.75 kg. No nicu stay and no o2 therapy. Birth history was uneventful. Corrected age is 10 weeks. She still hasn't attained head control . Head wobbling and lag is there. While on tummy time she is able to hold head at 45 degree for a brief period of time. She couldn't hold the head for long time. Rest of the milestones like social smile , cooing and movements are normal. Should I need to worry? Is this normal for preterm?