I'm going to break up with my boyfriend because he refuses to wear sunscreen.
Why do you want to break up with your boyfriend over sunscreen?
I'm worried that he will get skin cancer and become very sick since he won't wear sunscreen.
I'm sure you're very concerned about your boyfriend's heath and it's good to be concerned about it. Perhaps you can share your concerns with him and see if he will relent to wear it before you break up with him.
Well do you want me to get skin cancer?
Being concerned about your boyfriend's health is great, however, you shouldn't be pushy and expect him to do everything you ask. You should still respect that it's his body and he can make the choices that he wants. If you can't respect his choices then it may be best to distance yourself.