The cream you have been using likely contains a strong steroid mixed with an antifungal. While steroids quickly reduce redness and itching, they weaken local immunity, allowing the fungus to survive and rebound once you stop. To permanently cure this, you should consult a dermatologist. They will likely prescribe a steroid-free, pure antifungal cream (such as luliconazole or clotrimazole) and possibly oral antifungal tablets (such as itraconazole) for a complete course. Additionally, keep the area clean and dry, wear loose cotton clothing, and avoid sharing towels. This is a very common, highly treatable issue when managed with the correct, steroid-free medications.