Hi, thanks for asking in Healthcare Magic. Less menstrual flow is called hypoomenorrhoea where the blood loss is scanty and the menstruation lasts for only 1 or 2 days. Erratic and infrequent extension of of menstrual cycle exceeding 35 days is called oligomennorhoea. Most often this is due to thyroid problems. Both hypothyroidism (low thyroid hormone level) and hyperthyroidism (high thyroid hormone level) can result in menstrual irregularities. Other frequent causes are poly cystic ovarian disease (PCOD), obesity or malnutrition. Correction of the causative factor can solve your problem. Thyroid problem is sometimes associated with PCOD. In case of obesity, proper weight reduction is necessary. Correction of anemia and other nutritional deficiencies will also help. Cyclic administration of estrogen and progesterone will regularise the periods. Triphasic oral contraceptive pills (OCP) are given to maintain regular period with normal blood flow. Triphasic pills mimic normal hormonal fluctuation. Being an young girl you should not take it for more than 4 years at a stretch. Both estrogen and progesterone inhibit ovulation and progesterone ensures prompt bleeding maintaining a 28 day cycle period. Fertilization will return within a period of 6 months of stopping the pills. I hope this is useful to you.