This is 100% wrong. You need to talk with him. Tell him your desire for more children. Compromise on the issue.
He is dumb for thinking pulling out is going to not get you pregnant, but you should not be activly trying behind his back.
well he must not be that worried about you getting pregnant if that's the only form of "b/c" you're using. there IS sperm in the pre ejaculate. so eventually his luck of not getting you pregnant is gonna run out.
Wherever there's live sperm near the proximity of the vaginal opening... pregancy is possible.