Oligomenorrhea is the term for by light or infrequent menstrual periods. It occurs in women of childbearing age. Some variation in menstruation is normal. A woman who regularly goes more than 35 days without menstruating may be diagnosed with oligomenorrhea...Most often, this condition is a side effect of birth control pills. Some women experience lighter and lighter periods for three to six months after they begin to take the contraceptive. Sometimes, periods stop completely...Consult nearest gynecologists they will do the needful.