Took plan B on my period now I’m going on 8 days and it has not gotten lighter?

I got my period exactly 7 days ago (Wednesday) , I took a plan B 3 days into my period (Friday). My period usually lasts about 4 days and I’ve never had this side effect happen with plan B. Is it normal for my period to be this long? It’s a medium flow and doesn’t seem to be slowing down at all.

Starting to worry a bit. Has this happened to anyone?