Can i get pregnant 7weeks after having first bc my bf ejaculated inside the day i got my nexplanon in, a week after my 6week check up?

Nexplanon failure: Nexplanon, like many other birth control methods will take a week before being deemed effective. If you were ovulating at the time of insertion then you're definitely at risk of pregnancy and should get tested right away. A missed period would put you further at risk.

Doubtful: But there is always a minimal risk. Check a pregnancy test to check and be safe. Best wishes.