six years together & still not pregnant?

I have been with my fiancé for six years & have only been pregnant once (I miscarried) we have never been actively trying but haven't actually done anything other than the "pull out" method to stop ourselves from becoming pregnant. is it normal to have been together this long & not have a mistake? I will admit I'm not that sexual & it's a struggle for me now that we are trying to want to have sex so many days in a row, could our lack of sex account for my not getting pregnant? once we finally decided to try I got pregnant in September & miscarried before I was even four weeks! I'm just worried we aren't fertile?