Delay in periods can be due to pregnancy, hormonal imbalance, depression, anxiety or other psychological problems, malnutrition, polycystic ovarian disease, and side effects of some hormonal medicines etc. As your pregnancy test is negative then you should follow the doctor' s instruction. Cycloreg is used as one tablet three times a day for 10 days not for three days to induce periods. For your satisfaction, get pregnancy test in blood before use of cycloreg.