Part of being in a relationship is communicating. It’s essential. You need to be able to tell him how you feel about what he said. And in a healthy relationship he should be able to take what you said like a mature adult who deeply cares about you and learn from his mistake because he doesn’t want to hurt you anymore. Jokes aren’t jokes if they hurt the other person, that’s what we tell our kids. You’re not too sensitive, it bothers you and that’s allowed! And you’re allowed to set boundaries with others and let them know if bothers you. That doesn’t make you sensitive. But, he can’t know how deeply upset you were because you didn’t tell him and you hid from him just how upset you were. So you can’t expect him to know what does and doesn’t hurt you when you don’t speak up. It’s not fair to him to hide your feelings. How can he be the best boyfriend he can be to you if you’re not letting him in on all that you are, which includes feelings. Take this as an opportunity for personal and relationship growth. I know it’s hard to be vulnerable but if you really care about him and he really cares about you, the best thing to do is to open up with him.