Hi there, There is no substantial scientific evidence which holds Plan B ( levonorgetrol) responsible for the cysts formed in Polycystic ovaries. Also the fact that you had taken it 4 months ago, it is unlikely that it is the reason for not having your regular period. Moreover polycystic ovary is a multi system disorder which is seen in women, its cause is not known but, its also not triggered by any medication. Women either have it or they don t. The anovulation is just a small part of it it has many other manifestations, like acne, hirsutism, weight gain, infertility, and glucose imbalance predisposing to diabetes. You need to get a thorough evaluation including blood test determining your the cause of absence of menstruation. Tests like FSH,LH, Prolactin and TSH are required to know if any other hormonal cause which can be easily treated. If you do have PCOS after ruling out other causes, lifestyle changes and medications like metformin, and oral contraceptive pills, are useful in regularizing the period and reversing the effects. Hope this helps. Regards.