Implantation bleeding or period after plan b?

My guess from what I've heard about implantation bleeding, I would say no. But again I am in the same kinda situation. I should be starting my period this Wednesday but from some reason last week I had some spotting just for one day, very light pink. So my friend said something about implantation spotting so I've researched it a lot this week. And for the most part it's very light pink to a brown discharge that can last for a couple of days. Not to say that yours isn't but I'm trying to firgure it out for myself. The only thing with me is I am very faithful to my BC, every day before bed time. Occassionally I would miss. But I have only been on this pill for three months. I switched from ortho-trycyclen to tri sprintec. Well good luck!