is there something wrong with me??

me and my partner been together for almost 4 years for the first year i was on the pill and then i decised to stop taking it as i was getting bad side effects and also we decided that were gonna use the pull out method ( we know that we can still get pregnant but we dont mind if we do get pregnant) so he has been pulling out for 3 years and i never got pregnant also i will say that he is good at pulling out but if we were healthy so how come we still not pregnant? i know he pulls out but its been 3 years so it would bound of happened