He cheated on you because he was bored with you, so he tried to turn away from you and play with other women. However, it turns out that it doesn't feel the same if it's not with you. He's devasted when you left him, he can't live without you. He promised not to repeat his mistake again, he has also cut off with that other woman because he is really feel sorry, he wants you to come back to him. Seeing you happy without him was too much pain for him.