Plan b?

So I took plan B 8 days ago, and my period was supposed to start yesterday. I have had mild cramps here and there for the past week and my boobs have been sore. Today I started spotting and my cramps are way worse, I have backaches, headaches, my legs hurt somehow and I’m SO tired. So, I’m guessing that I’m starting my period as these are my normal pre-menstrual symptoms. Just need reassurance??