If you’ve never doubted your faith, I’d say you’re lying or you’ve never spent much time thinking about it. I suppose people of all faiths doubt whether their understanding of the world is true or not. I’d even say any honest atheist would have to have some doubt whether they can know for sure there is no God. Perhaps the most honest view is a skepticism to all certainty.
Anyway, Greg Boyd’s book on doubt is the best one I’ve seen for Christians who struggle with doubt. Too often we hear stories of people who asked questions at church and were told to just have faith. Dodging and avoiding questions helps no one, nor does striving for an impossible to achieve certainty. Have doubts? Read Boyd’s book.