Talk to a doctor. A doctor can evaluate you for low thyroid function and can talk to you about several other causes of irregular or heavy periods. Some of the treatments are hormonal. Birth control pills are a common treatment, but there are other options that preserve fertility (allow you to get pregnant.). And you may need to be evaluated for pcos (polycystic ovary syndrome), a common cause of irregular periods.
Contraceptives. Irregular periods are caused when your body's signals for ovulation and menstruation get confused by hormonal imbalances that can be related to your thyroid (TSH), pituitary (LH/FSH/prolactin), ovaries (estrogen/progesterone). Many external factors can affect the hormones: malnutrition, stress, obesity, for example. Hormonal contraception can help to regulate your periods, which is healthier.