I took Plan B 3 weeks ago, had the initial heavy spotting period after but then it returned again. Could I be pregnant?

My boyfriend and I had unprotected sex therefore I took Plan B the day after. It was one week before I ovulate but I didn't want to take a chance. I know with Plan B there is spotting that happens for a few days afterwards that's consist of redish, brownish and almost blackish discharge. But that happened almost theee weeks ago and then it jut reappeared yesterday and it is too early for me to take a pregnancy test because I haven't missed my period which is due in a week but will probably be delayed from the Plan B so I was just curious if that has happened to anyone else or if anyone knows about this. I tried Googling it but nothing seemed like this.