I am 18 year old girl and just recently noticed fine hair has been growing on my stomach. Why is that?

Fine hair growth. You may have poly cystic ovaries. That's why it's important ant to know about your menstrual history. Do you have hair growing in other peculiar places, such as your face? If your periods are normal and you are not particularly hairy i would say chances are you are normal.Fine hair can grow any where. A visit to an OB gyne mightbeinorder to get a clean bill of health.