Do you refuse to look at your hands? Because those play just as an important role in the process, maybe even more so.
This sounds like has the potential to create some really negative unforeseen psychological consequences. I get you're doing it to avoid the thought of PMO, but you're actually telling yourself subconsciously that you don't like who you are. You're creating an avoiding behavior that's telling you that if I don't look at my penis and I don't look at my naked body then I won't have the urge to masturbate. That may be true, but if you create a scenario where you can't look at yourself in the mirror anymore because you can't control your urges, you're going to create a problem that is likely larger than PMO. Your mind is going to start telling you that you don't accept yourself.
You're eventually going to have to be fine with being naked and not having the urge to masturbate. It might be fine short-term to get yourself out of a mindset, but be careful long-term.
My suggestion would be to really think about why these thoughts are coming up and start to re-program them in your mind. It's the basic concept of mindfulness. When the old feeling of PMO arises tell yourself this is an old urge that doesn't serve my mental or physical well-being. The problem isn't with your penis or your body in the mirror as another poster mentioned, the problem is with your mental associations and past behaviors.