Can i get pregnant on implanon? i recently had unprotected sex and he finished in me. it was 3 days after my last period.

Not likely : Implanon is a very effective birth control method. Of course there are exceptions but Implanon is a highly reliable method. Condoms would decrease the risk and protect your against stds.

Low chance: No contraceptive method is 100% effective but the combination of birth control use as well as having intercourse remote from the time of ovulation, your chances should be very low to get pregnant.