From John Donne's poems, what can we infer about his attitude toward Christianity?

As I understand it, John Donne became a clergyman late in life after his marriage. It was at that point that he began to write religious poetry and some have suggested that he began to regret the reckless lifestyle of his youth. It seems clear from his Holy Sonnets that he adopted some traditional beliefs of Christianity. In Sonnet #10 he affirms a belief in eternal life in the concluding line "Death, thou shalt die."