Was it my period ?

So I recently started my period on Jan 31, this is my first period with nexplanon. It was pretty lighter than usual, I suffer from really really bad period. To the point I would have to change my pad or tampon ever 2 hours. But this period was much lighter than that. Super light that by day 4, it was already spotting light blood. Now it’s day 9, and now I’m just spotting brown. Usually the brown spotting goes away by day 5-6. Is this my period or was it implantation bleeding ? (I had a negative pregnancy test 4 days before my “period”) came