It really makes me sad the way people think it's okay to jump in a thread like this and post "ewww that's where your poo comes out, yuckeee!" type stuff.
Aren't we all adults? Don't we afford every poster here the respect that they are capable of consenting for themselves?
OP, if you went ahead, I hope it went okay and you enjoyed it. For future reference, you might want to pick up some lube specifically for anal use as the standard ones can sometimes not last long enough or be thick enough (because the vagina produces it's own lube which is added to whatever you apply, but of course the rectum doesn't.)
I make sure I've had a shit at least within 8 hours, obviously have a shower as normal, and use an anal douche if you're worried about any poo coming out.
Anal should never hurt. If there's pain, you're in danger of damaging yourself, so stop. Anal needs to be at a much slower pace than vaginal. You will probably feel a stretching sensation the first few times, just like when you first started having vaginal sex!
Don't allow him to go - either with penis or fingers - from your bum to your vagina.
If you don't/didn't like it, don't feel under pressure to do it again. Some people like anal, some don't. There's nothing wrong with either of those two options, or in the middle ground of "yeah it's okay but I wouldn't want it every time."