Re: 18 year old hair loss??
I can understand your concern over your hair loss, and while I do not have a miracle answer, I hope I can help you work through this.
Hair is highly dominated by our genetics. What type of hair do your mother and father have, as well as your grandparents? While we normally put so much focus on male pattern baldness, us ladies also have our share of thinning and losing hair.
There are several medical factors that can precipitate hair loss, these would need to be determined by a doctor after doing some tests on your blood levels and a health history on you. If you have insurance, or medical care in your school's benifits, I would consult a doctor.
There are also products being developed all the time to fight female hair loss, that could be explored, but do your homework before investing in these products, as they have very different success rates, and can be expensive.
I hope this helps a bit.