Sex is always messy. Anal sex is messier than vaginal, but just like vaginal, if you do it right and you use protection, it’s all good! If you’re a germaphobe then don’t try rimming (tonguing ass). Germs aren’t a problem if you’re using protection and you don’t do stupid things like go from ass to pussy using the same condom…
Try to use the bathroom at least an hour before, have several condoms on hand for switching, use lots of lube, and take a hot shower after!
It’s always good to try something at least once. If it doesn’t do it for you, there’s nothing wrong with telling your boyfriend that. There are plenty of different things you can experiment with that doesn’t have to do with anal!