Thanks for the query.Betamethasone
is a strong steroid
It is not advisable to use it on regular basis.
You might have developed fungal infection
Use of steroid may aggravate it.
Please get a KOH mount done,
This can confirm the fungal etiology.
A biopsy may even be required.
Treatment can be with oral antifungals as well as with topical antifungals.
Please meet a dermatologist
for exact diagnosis.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.