Anal Help

So my boyfriend is really into anything to do with my asshole. He likes to lick it and wants to cum in my ass. But I hate him licking it and We can never get it in my ass. It is so painful and we have tried everything. Like lube and just starting off with smaller things like a finger or smaller dildo  but nothing will work. And we both end up super frusterated when it's over. But I hate doing anything with my ass. Any advice?