Asking bf to go down on me(?)

I always go down on my boyfriend and I enjoy it. But I want him to do the same for me. He's mentioned it before but he's never attempted it and I feel rude if I tried asking him to do it. I just don't like asking for things a lot.

And I've tried dropping hints like sending him sexual pictures on instagram or text that reference to eating a girl out but he's terrible at catching hints!

Then I start to get self conscious when I want to just tell him because I start to think all the what ifs like:

·I smell down there,

·he doesn't like the way it looks,

·he doesn't want to do this,

·I'm forcing him into it.

I'm having trouble with all this, any advice?