How to feel good?

So I don’t send to many pictures of certain things to my boyfriend. I just don’t have to body too. But today I wanted to do something for him and try something new. He said he would like a mirror picture of me in a bra. But he said if I don’t feel comfortable to not do it. He wants me to feel confident about my body. I want to do it but I don’t know how. I’m are the big side and there’s no position to make me look sexy or at least decent in just a bra in the mirror. What should I do? Is there any other sexy pictures I could do?