You have said that you know it is totally wrong, so I feel that you already have the answer to your question. You shouldn't allow the relationship to go further until you are both single. Unless he leaves his wife, there will always be three in the bed, as she will always be in the back of your mind. This will be devastating for your self esteem. You seem like a strong person ... stronger than the urge to be with him. The best action to take now that he is sending pictures is to ask him outright what his intentions are. Let him know that you are interested and attracted, but that you are not prepared to start anything while he is married. You will be able to gauge a lot from his reaction, and it will give you a better idea of what kind of person he really is.