Your fungal infection is likely not improving because your current treatment includes a steroid (dexamethasone), which can actually worsen fungal infections by reducing the skin's natural ability to fight the fungus, while medicines like cetirizine and Avil only help with itching and do not treat the infection itself. For proper treatment, you should use a good antifungal cream such as those containing luliconazole, sertaconazole, terbinafine, or clotrimazole, and avoid any cream that contains steroids unless specifically prescribed by a doctor. Apply the antifungal cream regularly as advised (usually once or twice daily) and continue for at least 2-4 weeks, even after the skin looks better, to prevent recurrence. It is also important to keep the affected areas clean and completely dry, avoid tight clothing, and reduce sweating as much as possible. If there is still no improvement after proper use of antifungal treatment, you may need oral antifungal medicines under medical supervision, so consulting a dermatologist would be the next best step.