You can't control how your BF acts, but you can control how you react to his actions. Does he understand how much it means to you that he not sleep with his wife once he's told you he's not going to? He may not realise you see it as a big deal, and if you don't tell him he won't know.
If he does know how you feel about it and did it anyway, you need to ask yourself if you really want to be involved with someone who cares so little for your well-being. This is where your control of your reactions comes in. You can choose to put up with it - which means you're teaching him it's ok, or you can choose to do something about it - which shows him it's not ok.
"Something" may be anything from talking to him about the issue all the way up to removing yourself from a situation you no longer find to be joyful and/or safe.