hello. Welcome to HCM.
There can be numerous causes of rashes on skin. Diagnosis in dermatology should mostly be based on clinical examination which is the most important followed by other investigations as required by dermatologist
Now that you have tried local antifungals and have not responded, it is better if you go in for a dermatological check up and be treated accordingly. With an inappropriate treatment, the rash will keep on increasing and recurring.
Hope this advice helps.