Are you eating enough protein and taking a multivitamin?Are you or have you gone through a recent hormonal change (menopause or pre-menopause)? Have you recently gone through something stressful or tramatic (death in the family, surgery, etc)?All of these things can cause it. Remember, hair is in a 3 month cycle so whatever you were doing roughly 3 months ago is usually what is causing it. At your age though, my best guess would be hormonal. For women, that is the cause a lot of the time. Even going off birth control pills can do it for younger women.I would suggest taking hair, skin, and nails vitamins and taking the herb Dong Quai if it sounds hormonal to you. Also, there is a chinese herb called Ho Shu Wu that might be effective.