What is the major conflict John Proctor faces in Act III regarding saving his wife ?

In Act III, Proctor has come to the court to argue that Abigail and the other girls are lying when they accuse others of witchcraft and pretending when they behave as though they've been bewitched.  He wants to prove his wife, and the wives of his friends, innocent, but, to do so, he will have to offer some proof that Abigail has other motives than to cleanse the community of evil.  The court's position is that God is speaking through the girls, and so compelling evidence is required to prove that this is not the case, and that Abigail is, in fact, manipulating the judges and community in order to get rid of Elizabeth Proctor.  However, in order to prove his wife's innocence and his former mistress's guilt, John will have to reveal to the world that he cheated on his wife and slept with Abigail.  He does not want to have to do this because he is deeply ashamed of his conduct and realizes the importance of reputation (this information will tarnish his reputation quite a bit).  Thus, he is conflicted about confessing the truth and saving his wife because he does not want to have to reveal his misconduct.