Why is my head tilted to the left?

is this some kind of abnormality? eversince i was a kid, my head seemed to be tilted to the left.i don't feel that my head is somewhat heavier to the left,but i just feel comfortable on that position.so whenever im listening to something, thinking about anything, or taking a pose for photographs, they always tell me to make my head on a normaL way. please help. someone please enlighten me...