Anal????

So my sexual partner wants to have anal Sex (we've done it once but I wouldn't let him come in me) and this time we wants to come in me. My two issues, 1: what should I expect? Like I feel like it would be super messy... is it gonna ooze out? (Sorry I'm inexperienced when it comes to anal 😅) and 2: I'm not on BC and I've read where if it goes south it can get into your vagina and possibly cause pregnancy (yes I'm aware it's extremely rare but it still freaks me out!) any tips for that??

No negative comments please!