In chapters 10-12 how does Dimmesdale feel about himself? "The Scarlet Letter"

With the character of Arthur Dimmesdale, Hawthorne introduces the concept of psychosomatic symptoms as the Reverend holds his heart and, as is later revealed, has a letter "A" raised upon his chest.  Dimmesdale's health is deteriorating because of his desperate guilt.  When he attempts to confess by calling himself a worse sinner than anyone else in his sermons, the congregation interprets his words as saintly humility and regard him even more highly than previously.  

In his desperation, Dimmesdale turns to self-flagellation to punish himself.  But, this action does nothing to soothe his soul.  So, in Chapter 12 he walks "in a shadow of a dream" to the "spot of public ignominy," the scaffold where Hester once stood.  There is overcome with

a great horror of the mind as if the universe were gazing at a scarlet token on his naked breast, right over his heart.

Dimmesdale's shame evolves from his feelings of guilt because of his tremendous hypocrisy.  He, more than any other character, personifies the evil of Puritanism's refusal to forgive the sinner, causing a greater evil, that of the worm of hypocrisy which eats away at the soul.