Weird

I recently wanted to try anal with my boyfriend, and im not sure what to do. I'm afraid about if he fingers me and there's sh*t residue. Soooooo um, how exactly do you clean out the bowels or to make sure that there is no sh*t left or something? Im do sorry about asking this, just really new to this, and any advices? Is it possible to get pregnant from the butt? Like if he cums in it or something?