Why does anal sex hurt so bad?

Loogencia • Love
My boyfriend and I almost 5 years tried to do anal sex a few months ago. It was something we both had never done and I was very willing and excited about it. He used lube and was gentle but it hurt too bad. It was an absolute terrible experience. Too much pain for me to handle, it made me lose my sexual appetite for the night completely. Although my experience was not pleasurable, I am still curious and would like to try it again. Our aniversary is coming up and I would like to surprise him by trying again. Any suggestions on how to not make it hurt so bad? By the way!!! I am NOT doing it "just to please my man" I would like to try again because it is something that I would like to experience the way most others seem to. Thank you so much.