yes. plan b pill doesn't really work for everybody. just wait two week to take pregnancy test.
Since you took the pill within 72 hours of the unprotected sex, I wouldn't stress about it. Stressing can actually cause your period to be late. Also, the pill does different things to women's bodies. I took it one time and immediately started bleeding within hours for my normal days of my cycle and didn't get it until a month and a half later. I personally think it messes with our hormones, but it does work. Try not to stress out about it. You should be fine!