Just a question if anyone could help

According to glow my AF is due 12/19 I started lightly spotting on 12/14 I was thinking maybe it's coming on early that pink went to brown over the next couple days and then on 12/19 there auntie flow I'm assuming because I started bleeding very heavy...what could this be could have had implantation bleeding right before my period and still get my period. Any thoughts someone help me. My periods as requested usually on time not late or early what should I think