Possible chance of preg? Against birth control!

I'm completely against birth control! I don't think it's right to take a pill that's full of chemicals to make your body do something that it's not suppose to do? I let my body do what it's naturally suppose to do. I have never even tried birth control once. My husband and I always use the "Pull out method" he never cums inside me. And we've been together for a couple  years. Have not had any possible pregnancies. What's the likelyhood of me really getting pregnant? And why do you think I have not gotten pregnant yet?