Oral sex?

So I am very open to my boyfriend about what I want to do during sex or if I want to try something new with him... I've been asking him if he'd eat me out but he respectfully turns me down and says, "I'm not about doing that.." But when I've asked if he's ever done it before he always tells me no so I asked him if he could just do it once and if he doesn't like it he never has to do it again but he still says no. I've also asked if he won't do it becaue he feels like he might be bad at it but he says no... Has anyone else had this problem & if so any tips? I fully respect his boundaries because he respects mine, but if he's never done it before I wish he would try it at least once