preparing for 1st time anal?

Me and my boyfriend want to try anal? We are very comfortable with each other and have done everything else. We have tried fingers up the bum. However he wants to give me anal, now I am scared abit of it hurting and the whole rumour of pooing. How can I prepare, shall I get a anal cream/spray/lube sort of things like the Ann summers anal play? And how do I make sure I don't poop? I know that sounds grim but I know a lot of people feel like they will and sometimes have. How will I be fully