Anal sex

So my S/O has been urging me to spice things up in the bedroom (using toys, lubes, new positions, etc). I’ve always wanted him to give it to me anally but he can’t get over the fear of getting poop on his penis. How can I ease him into it? I have essentially offered it on a silver platter and he refuses! I tell him how badly I want him to just stretch me out and tear up my booty but he won’t bite. Tbh I’ve become so uninterested in vaginal sex and can only get off if he plays with my butthole during. No matter what position we try, it doesn’t do it for me unless I am getting anal stimulation. I swear it’s like he just TOUCHES my butthole and I’m soaked. How do I convince him to just take the plunge and dive right in.

PS. I keep it really clean, he will eat it but won’t actually go INSIDE