Hi, Menstrual irregularity can occur due to many causes which will affect the reproductive hormone levels like: -Psychological factors like stress and strain -Changes in daily activities like diet, sleep, weight,etc. -General conditions like anemia, fluctuation in blood sugar levels, thyroid abnormalities, abnormal serum prolactin levels, etc. As all your home pregnancy test kits gave negative results, the possibility of pregnancy is very less. By clinical examination and investigations like hemoglobin levels, blood sugar levels, thyroid profile, serum prolactin levels and ultrasound the possible cause of your problem can be identified and treatment can be taken accordingly as suggested by your doctor. After analyzing the reports you can take tablets for withdrawal bleeding with your doctor s advice. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Sree Gouri S. R., OBGYN