Seneca, Aurelius, Epictetus are stoics that have a lot of Christian parallels in terms of how to live and view your place in the world.
What got me through my existential crisis was Nietzsche, Kierkegaard, and Camus. Kierkegaard might be good for you as he talks about the religious life as the highest form of living. If you don't want to lose your faith, I wouldn't read the others though.
Outside of that there's people like Emerson and Thoreau