How to prep for Anal sex

So, this weekend I've agreed to have anal sex with my BF. I'm excited to try but scared I might crap lol. We have tried it in the past but it hurt so much and I couldn't relax for it.  I've been watching porn, keeping in mind for lives to try, slowly using my fingers on myself, and trying to use a breathing technique. What are more tips or advice to help me??