Some people just have tendencies toward doing this sort of thing. I used to be really bad about needing to be overly clean, too. Instead of showering multiple times a day, I used to take showers that lasted 1 hour-1 1/2 hours long every day. I would scrub methodically in the shower to make sure I was as clean as anyone could ever get...and then some. I would even have to scrub each section of my body a certain number of times. If I didn't, I didn't think I was clean.
It got so bad that I would end up running all the hot water out and spend 40 minutes or so in ice cold water. After I dried off, my skin was so dried out that my back, stomach and arms would become covered in tiny little splits that burned like crazy. I never wanted to put lotion on, because it felt like I was greasy then, and dirty. I even was so uptight about shaving my armpits that because of the already dehydrated skin I had, they would end up bleeding after I shaved them, and it hurt so bad for hours it drove me crazy.
There came a time when I started feeling so trapped and frustrated by my cleanliness compulsions that I just became really angry one day. I had enough. I just told myself that what I was doing was stupid and pointless. I was sick and tired of being trapped into a routine like that by my own inability to control my mind. So, that day, I just said enough is enough, and I'm done. Period. I went and took my shower then, did it completely differently that I used to, and only took 30 minutes in the water. I realized that nothing bad happened as a result of my showering differently, and that I felt absolutely liberated. I have never looked back since.
I know that all this sounds silly to some people, but it is a very frustrating thing to go through. Just know that if you allow yourself to get fed up with it, and start training yourself to think that what you are doing is pointless nonsense...even if it doesn't feel that way.....you can get past it!