Plan b pill question?

So in the beginning of August me and my partner had a slip with the condom and we decided it was best to take the pill . A week and a half later the same thing happened and I took the pill again and now I'm 4 days late on my period and have light cramping . The weird thing is that the first time I took the pill I had this weird brown discharge and this second time nothing . Idk what to do ? Is this normal ?