Hi, Petogen injection contains Medroxyprogesterone, which is used as one of the contraceptive method. As you have not taken the second shot after first injection the possibilities are: - Bleeding due to the withdrawal effect of the progesterone, sometimes this can be prolonged in some women. As you have not used any contraceptive method the possibility of pregnancy also cannot be ruled out. So, to come to a conclusion, please go for an blood test for pregnancy, which can give more accurate result compared with a urine pregnancy test. If the serum beta HCG levels in blood test shows less than 5 mIU/mL, the possibility of pregnancy can be ruled out and the bleeding can be considered as withdrawal bleeding only. Then, with your doctor s advise you can go from anti-fibrinolytic drugs to control the bleeding. And possibly your cycles may regularize soon. If the irregularity persists, you may need to get evaluated by undergoing investigations like hemoglobin, blood sugar levels, thyroid profile and ultrasound. With this the possible cause of irregular periods can be identified and treatment can be taken accordingly. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Sree Gouri S. R., OBGYN