You simple have to be honest with him and tell him that you will not be sending nude photos via text. Sending photos can lead to others having access to the photos and depending on your age, it’s against the law. I advise you to stand up for what you want and if he doesn’t support you, then perhaps he isn’t the right boyfriend for you. Not sending nude photos doesn’t mean he will like you any less… it means you respect yourself and your body and are confident in communicating how you want to be treated. It takes a lot of courage to do this and I congratulate you on writing in and asking for advice. Good luck!