Greetings Madam. First of all glad that i can be able to help, guide you in overcoming your confusion about I-PILL. Some Facts to Know about I-Pill: 1. I-pill is a single-pill emergency contraceptive that offers you an effective way to prevent an unplanned pregnancy viz., prevent a woman from becoming pregnant after she has/had unprotected intercourse. More than 80 % effective in preventing pregnancy after unprotected sex. 2. I-Pill works by following way viz., altering the lining layer of uterus, prevents release of an egg from ovary, prevents sperm from reaching egg by making cervical fluid thick. 3. Remember, I-Pill is not an abortion pill. Normally Sperm survive for 5 days in Female Genital Tract but Egg maximum survival time is just 1 day. So Best chance of getting conceived occurs when intercourse occurs 1-2 days prior to egg getting released from ovary viz.,11-13thday from beginning of menstrual bleed. Yes, it might cause your next period to come early or later than normal. Small amount of bleeding is a temporary effect of I-Pill. Also if your period does not come within 21 days of treatment, you may be pregnant and you should check this one with a pregnancy test.Here in this case as you have mentioned PREGNANCY TEST was negative & period not started, it means either 1. You ll get your period little late due to irregular cycle/due to body condition/hormone dysfunction/ altered hormonal regulation/obstruction/any other cause (or) 2. Still you are Pregnant. Repeat PREGNANCY TEST to see if NEGATIVE again. Best advise is to clear your doubt from a OBGYN / General & Family Physician by doing an ULTRASOUND SCAN & other necessary test & confirm. Note: Finally it s just a guidance. Not a definitive treatment as i haven t seen you personally. You ve to realize that these are temporary remedies. We don t know what your exact condition is unless we see you personally.Consult your Doctor/OBGYN if you still feel uncomfortable in spite of knowing above possibility. Hope i guided you right & it helped.