Well for one, I don't know why you weren't using a condom while getting a girl up the ass. Do you realize how much bacteria and shit (literally) is up that poop shoot of hers? And that possibily getting inside your penis/urethra, possibly giving you an infection? I mean, it's a chance you take. I've done it before without the guy wearing a condom and he had to make sure to wash up really good and take a piss afterwards.

As for the poop, it's normal to have a little bit come out when you're finished. Especially if you've been going at it hard. Just makes sure she's taken a good shit before you try to ram her in the butt.. but even then it's still possible for some crap to come out with your penis. Cheers!