Hello Thanks for your query. Mifegest kit is supposed to be used for early pregnancy termination. It is never supposed to be used without medical supervision. Also, if your pregnancy test is negative, there is no point in taking that kit. There are various reasons for irregular periods. Stress, anxiety, thyroid disorders, frequent travelling, weight loss or gain, polycystic ovaries, endometrial hyperplasia - these are all possible reasons. You have to consult a Gynecologist to know why you have missed your period. Please do not take any medication on your own, or it will cause further complications. Take care.