I would try an antibacterial soap (like cetaphil) and then applying tretinoin to spot treat. This way clothes or sheets arent stained.

Also, make sure you wash your your clothes constantly. Try not to wear anything two times in a row without getting it washed. Get your sheets washed once a week too. And although you might prefer thongs, sometimes its better that your butt rub up on smooth cotton undies rather than tight denim or other kinds of material. That is my two cents.