For persistent fungal infections on the back and private areas, over-the-counter topical creams containing clotrimazole, miconazole, or terbinafine can be very effective. Apply them to clean, dry skin as directed. However, because your infection is widespread and persistent, you may require prescription-strength oral medications like fluconazole or itraconazole. Keep the affected areas clean and dry, wear loose-fitting cotton clothing, and avoid sharing towels to prevent spreading. Please consult a doctor or dermatologist for a proper evaluation and a tailored treatment plan to safely and effectively clear this up.