I am a 22 year old female. I had my periods on the 2nd of this month. I had unprotected sex on the 10th and took a tablet of Unwanted 72 within an hour of having sex. After five days of taking the tablet, I experienced spotting for two days and very light bleeding on the third day. I have not had my periods since then. What are my chances of getting pregnant? If I am not pregnant, when should I expect my periods? Should I count my cycle from 2nd or 15th, that is, the date when I experienced light bleeding due to pill? Also, could the bleeding that I experienced be implantation bleeding since it was too less? I also took a home pregnancy test on 21st that gave a negative result but I am not sure if I can rely on it. Should I take another pregnancy test?