My pediatrician ..didn't subscribe vit D3 till 5 months of age I don't know..how he forgot Am extremely tensed .. He is 6.5  months old now..he can sit with his own body support for 30 secs mayb Can't roll His neck is unstable while sitting But on the shoulder his head is quite stable can move head side to side We have lil or absolutely no exposure to sunlight . He was fully breastfed baby..and now is having meals once a day . He is very active . already teething ( can see one teeth out) What should be done