My bf masturbates in the bathroom when I'm home

This bothers me so much, and I know it shouldn't. My bf and I have a really good relationship, both emocional and sexual. My problem is not that he masturbates, my problem is that he's doing it when I'm home and in the next room. Like why!? I'm right here, just do me!! This messes up with my self esteem because I don't feel desirable or wanted. Like he prefers his hand instead of my body. We do have a healthy sex life, and we have regular sex. So this makes me feel like I'm not enough... I don't know how to deal with this. I address this issue once in the past and he got defensive and told me that I didn't understand and it has nothing to do with me. But I still feel hurt, because I'm waiting in bed for him and he take 45min in the bathroom with his ipad doing "number 2" right..