Irregular periods can be caused by various different disturbances in the reproductive endocrine system. The first question I would ask you is how much you weigh and if you have had any weight gain or weight loss
recently. Women that have low body weights often have irregular periods and can go 3-6 months without having one. If you are involved in regular intense exercise, this can throw off the hormonal cycles and make your period more irregular. Another possibility is that you have polycystic ovarian syndrome (PCOS). Besides the development of ovarian cysts, this syndrome also results in irregular periods, weight gain, diabetes, and also abnormal hair growth pattern called hirsutism. If you think this describes you, then you should be evaluated for this. Other possibilities exist as well that would need to be looked into by your doctor
I suggest that you schedule an appointment with your primary care physician
or OBGYN, whoever you see for your feminine health. Bring with you a calendar of your periods so that the pattern can be mapped out. You doctor may want to get some blood tests for certain hormone levels. If the current birth control that you are using is not regulating your cycles, then you may need a different hormonal formulation.