Need your opinion on anal sex.

Hi , I need to hear you guys opinions on something . So when I am about to have anal sex I do my best to make the best out of it . I go to the bath , shower , clean up . Although when I have anal sex I always feel like if I let go I will "Poop" Sorry if that's gross. Thing is since I don't let go I can't concentrate on the feeling or relax at all. In the ending all it does is hurt and I have no pleasure in the end . What am I doing wrong?