my son is 16 months and a few days old. last week he stood up on his own and walked a bit. but after that day he just stopped that. he starts crying if we encourage him to walk on his own or stand. he walks(in fact runs) if we hold his one hand. but he seems to be scared to walk on his own and I feel he seems a bit shaky when trying to walk. he is on calcium and vitamin supplement. is this something to worry about