Implantation bleeding?

Hey everyone, I'm new here.  I've been TTC for three months now.  I had sex multiple times during my fertile window this past month.  I even took an OT on 10/19 and it was positive.  We had sex that day and two days after.  Period is due tomorrow 11/3.  I had light spotting ( barely there) on and off Tues-Friday.  It was a dark brown color and only showed up a few times after wiping.  It stopped Saturday morning.  My breasts are killing me!  But I don't think my nipples are darker.  Could I have experienced implantation bleeding?  When should I take a test If period is due tomorrow?