1. He may really be expressing his mistake and feel that he should not love you. This situation may be caused by some conflicts between your sense of responsibility and values.
He may be sarcastic, which shows that he actually loves you, but for some reason, he wants to express his feelings for you by saying "wrong", which may require you to know more about his heart.
In either case, you need to know his real intention according to your relationship and context, and you can communicate with him directly if necessary.