I have a bad habit of taking a long shower after everytime I crap. How do I stop?

Well... I guess it started one day after I had an upset stomach after eating some greasy, powdery crap at school. Ever since then I just felt an almost desperate urge to take a shower every time I crap, which I do. But the problem is, what if i gotta go at a public place or something? What am I supposed to do then. And suppose I can't hold it. How do I get rid of this "need to shower" thing?