my age is 15.请问这句话从语法上讲是对的吗?在英语国家会这么说吗?

my age is 15.请问这句话从语法上讲是对的吗?在英语国家会这么说吗?
语法上没有错,但是最好要写成下面句子
（1） I am fifteen
(2) I am fifteen years old
(3) I am fifteen years of age
(4) I am the age of fifteen
(5) I am at the age of fifteen
(6) I am 19 years of age
（7） It is 19 years since I was born
(8) I have been in this world for 19 years