Thanks for the query. 3 weeks is a reasonable time for a fungal infection to get cured. Fungal infection is very common and was very easy to treat. With rampant usage of antifungals, the fungus has become stubborn. There are various ways to deal around the situation but first see a Dermatologist for reestablishing the diagnosis. Once confirmed, treatment can be initiated. Don't worry it will resolve for sure if you correctly follow the recommendations. Hope it helps.
Next Steps
Meet a Dermatologist. Keep the area dry.
Health Tips
After touching the area with ringworm, wash your hands before touching another area of your body. Avoid sharing towels and other personal items