HELP IS HE CHEATING ON HER?

It states in the Bible that he shall find no comfort in any other woman than that of his wife. If they are married, took vows, meant them, yes, it is cheating. He is still entertaining the thought in his head which is the same as just doing it. Some may disagree, but, it depends on the true marital commitment and beliefs in their union. If she was doing it to him, he would feel just as bad and wronged.