Is it on? Or not?

So Af was due on this past Sunday. When I woke up that morning I was spotting, so I figured that by the end of the day I should be fully on and I proceeded to get my supplies for the week. But it’s been two days now and I’m just spotting, not even enough to soak a tampon fully or a pad for that matter. This month was a bust month for me and SO and we did have sex before and after I ovulated. It’s day two of my cycle and still just spotting. Could this be implantation bleeding?