Anal fear! TMI maybe?

Ive NEVER done anal bcuz ive always been disgusted by it, but my long term bf likes it and has asked me once and i said no and he never bothered again. Ive been away from home for a month now and ill be going back in a few weeks, one time we were sexting and i got EXTRA horny and told him to fuck me in the ass, he got so excited omg😂 he was like omg seriously?? I was like uh yeah.. he was like r u sure? And i said yes (yeah im convinced i want to) so when i go back and we have our first night together since a long time, we will get down to it.

SKIP TO THE QUESTION :

I'm actually afraid of shit coming out on his dick or smth (ive heard this from one of my friends)

I'm very hygienic and i shave my anus too and everything and im pretty clean.

I dont know what to expect tbh so i dont want any surpise shit🙃

Is there anything i could do? Anything i could eat? A way i can clean inside of my ass? How to prepare? Prevent shit odor? Like im so nervous and i want it to be clean and perfect!

Also, hes HUGE, any positions that hurt less?