pregnant on birth control?

I have had the implant for a long time now. me and my boyfriend have sex pretty often, and we don’t use a condom because I have the implant. He often wants to finish inside me, knowing that I could get pregnant but he says “i’m on birth control” so it’s okay. He never has because he respects me not wanting him to, but if I were to let him what are my chances on pregnancy?! Is it high with the implant?!