We went through something very simular with one of our cats and after numerous trips to the vet it was finally discovered that she was having an allergic reaction to something in our new home. It's a bacterial reaction that will only get worse if left untreated. Mine had washed her tummy to the point that she had welts from the constant bathing. She was treated with a cortizone shot to help control the allergic reaction and a topical spray called Genesis Topical Spray by Virbac from my vets office. The bottle says for topical use in dogs only but we used it twice a day for about 10 days and her stomach and tail cleared up completely with no reaccurances.
I hope this helps. Please let me know if you need further information.
__________________
If you found this answer helpful, please click on ACCEPT and PLEASE LEAVE FEEDBACK. Accepting an answer that you are able to use improves BOTH of our ratings. And a bonus is always welcome! You may reopen your question at anytime if needed.

