Thank you for your question. Common causes of rashes on the groin include fungal infection, eczema and intertrigo.
It is important to make the correct diagnosis as the treatment for fungal infection and eczema is very different.
As your rash has been very persistent, you can consider seeing your dermatologist/doctor to confirm the diagnosis. A fungal scraping can be performed to confirm or rule out the diagnosis of fungal infection if there is any doubt.