Hello,
It looks like intertrigo skin due to fungal infection. Keep the area dry and keep a separate towel for yourself. Also use mild soaps and wear cotton clothes. Most forms respond to over-the-counter products, which contain any of several basic ingredients: miconazole, tolnaftate, terbinafine, and clotrimazole.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
It definitely sounds like yeast. Have your dr look at it and most likely will prescribe you some nystatin powder or cream. Should take care of if!