Being under weight can also be the root of the problem for younger females when their cycles are not regular... my niece, when she was around seventeen years old and not sexually active, had to put on fifteen pounds when her cycle wasn't regular and her period was only taking place once every three months... now three years later she is doing fine - and her doctor said females need a certain amount of body fat to have regular cycles.

Making a doctor apt is the only way to go here... ((( hugs )))