How I can purify my physical body?

I don't like the shape of my body. My skin is poor. I lack physical stamina and strength. I feel hungry but I don't eat. I just don't like myself. How can I purify my body so that I feel good in it? My body is just lethargic, fatigued and weak. Did Buddha share any techniques to purify and strengthen the physical body? Also I masterbate a lot which is the cause of my weak and ugly body. I don't even have the strength to exercise the way I want. This is all topped with immense guilt that I want to wash away.