Boyfriend is addicted to Hotwifing

My boyfriend and I have been together for almost three years now. Around 5 months back he revealed that he's been wanting take part in hotwifing. This would involve sending pictures of me (explicit and not) to people and getting off to it together. I don't want to agree to this. I cannot really. He tries his best to stay away from it and not ask for it but the temptations grow increasingly bad. He is currently under a lot of stress and tension, is possible depressed but cannot get a formal diagnosis because his parents do not believe in mental health. He is trying a lot to not let this get between us, he wishes everyday that he didn't have this need. But its worse when one of the only thing that makes him feel relief ended up being this. I dont know what to do to help. I hate saying no to him and everyday I want to be okay with this but the moment I close my eyes and imagine that I feel disgusted with myself and hate myself. Please any help at all on how to cope with this would be appreciated. Thank you for reading this far.