How does John contradict himself when he is alone with Abigail?
After Elizabeth has kicked Abby out of their house, suspecting the affair with John, Abby claims that John has continued to imply that he still wants the affair to continue, John denies this. Then Abby says she has sensed it and has seen John looking up at her window. John admits to looking. This is meant to illustrate that John has at least given Abby gestures or nonverbal indications of his lust for her. It would be best for him to apologize for the affair. He is the older man who has taken advantage of a younger woman. But instead, he gives her confusing signals, saying he will not see her again, but that he still has feelings for her:
Abby, I may think of you softly from time to time. But I will cut off my hand before I’ll ever reach for you again. Wipe it out of mind. We never touched, Abby. (Act 1)
She replies that they did "touch." John replies that they did not. Proctor is trying to put the entire affair out of Abby's mind. So, he says "We never touched, Abby." It is his way of persuading her to pretend that the affair never happened. This is confusing and frustrating to Abby. Recall that both of her parents are dead. She is lonely and when John has the affair with her, she finally feels loved and is desperate to continue to feel loved. John should have realized this before the affair began. He contradicts himself by telling her to put it out of her mind, but then says he thinks of her "softly from time to time." There are too many mixed signals for Abby to handle.