Nathaniel Hawthorne's novel The Scarlet Letter is rich in the complexity of the human mind. Dimmesdale is a central element in Hawthorne's examination of what drives a man to what most would consider madness.
Chillingworth's discovery in Chapter 10 would appear to be the catalyst of Dimmesdale's torture, both physical and mental, but his descent begins much earlier than this. Chillingworth has had strong suspicions since he witnessed Pearl bestow a kiss on Dimmesdale's hand at the Governor's Hall in Chapter 7. From his comments about looking at the physical features of the child and seeing who she favors to his probing questions about the nature of secrets in Chapter 10, Chillingworth is merely fueling the fires of Dimmesdale's broken psyche. We can see Dimmesdale struggling with his guilt as early as chapter two, when Dimmesdale has to question Hester about the father of her child. He seems nothing less than relieved when she refuses to divulge the information the public seeks.
The most telling indication that Dimmesdale is feeling the pangs of guilt without the assistance of Chillingworth is Dimmesdale holding his hand over his heart. This mannerism is maintained through the course of the novel and even with the knowledge that Chillingworth has discovered his secret, he seems to find little relief until he grapples with his inner demons and confesses his secret at the conclusion of the novel.