How long does Implanon really work for?

Patient: I was on a birth control called Implanon. my 3 years of using this birth contrrol was up about a week and 3 days ago. About a day ago i had unprotected sex. is it possible that im pregnant. because i read this article that says that implanon actually is effective for 4 years. And the insertion is out of my arm yet. I couldnt make it to my appointment. I really need your help. I feel myself panicing and i dont know what ill do if I end up prefnant.