I just came across a guy who discusses doubt to a great degree as it relates to Christianity. He categorizes it into three types and discusses what those are and how to deal with them.
Here is his four part lecture on doubt.
Tugging at Our Hearts: The Biblical Imagery of Heaven
Is God Ignoring Me? Making Sense of God’s Silence
He has many other interesting lectures and you can visit his web site at http://garyhabermas.com/