i had implanon after having a my son, and every month for the 12 months i had it in i got my periods, even got bleeding every 2-3wks and would bleed for 2-3wks.....This has also happened with my sister who got the implanon too, so not everyone who gets the implanon stops getting their periods (also my sister doesnt have children yet)

I would maybe do one more test if still a BFN then i would assume its a negative