Plan B

NS
I have been reading a lot about Plan B which is my area of concern however your posts helped me a lot. I had sex on 14 Jan and took plan b on 15 Jan and as said withdrawal bleeding started on 20 Jan and lasted till 23 Jan. My periods started on 9 Jan and ended on 12 Jan. So I just wanted to know out of experience what are the chances of pregnancy as I am really worried.... N