I am 21 and am not sexually active. i had my period almost three weeks ago and it still has not stopped. i am really worried.

Not normal : See your gyn, menstrual flow for three weeks is not normal. Many possible explanations for this that your doctor will explore to help you.

Not likely scary: Without the threat of pregnancy at your age there are few really scary concerns. Sometimes the prolonged period is from stress and hormonal changes. Other times it is from a small polyp or finger like growth that tends to easily bleed. These can be in the cervix or the uterus. Still other problems are infections of the cervix like chlamydia or gonorrhea if you have had sex in the past. Get checked.