Sex and BC

So I'm on birth control and have been with my boyfriend for almost two years.  We stopped using condoms about four months ago. I still don't let him come inside of me because I'm scared of getting pregnant. Is it possible to get pregnant even while on birth control. He really wants me to let him but I'm just scared. Lol I'm 21 and like I feel like I should know the answer but I've never asked anyone