NSFW My bf keeps trying to talk me into having anal sex with him despite my repeatedly saying I don't want to. What should I do?

I just find it really rude and selfish of him.
I feel like he has no regard for my feelings, as though he thinks he has some kind of right to treat me as a sexual experiment.

When I ask him why he wants to do it, he just says,because he has never tried it before.

I think anal sex is weird and unnatural, I just don’t want to do it.