Implantation late

Is it possible to have implantation later like...est 16 days after ovulation. My bbt showed ovulation but my strips didn’t that day or day after and I stopped testing🤦‍♀️ we BD to be safe. Anyways i was due for my period which is irregular to begin with so due date was est. I’ve tested but bfn but last night and this morning it’s just a slight amount of blood not bright red more like old period blood brownish in color.