What Causes Burning Pain In The Vagina And Rectum Of An Elderly Person?

My mom is 84 years old and has been experiencing a burning pain in her vagina and rectum area for about three weeks. She has been to the emergency room twice, they gave her an antibiotic figuring it was a bladder infection. She was on it for one week. The burning pain did not go away. She then was told she may have a yeast infection from the antibiotic and was given a cream (even though the burning was there before she took the antibiotics). It has been three weeks and she is still suffering from the burning sensation in both areas. She also has problems eating as she says the food stops in her stomach and won t digest. She has history of diverticulitis and was hospitalized three years ago, no surgery. The doctor feels that she may not be getting enough blood flow in her large intestine but no one has been able to give us a clear diagnosis. She has gone for all her blood, urine and stool testing and there is nothing showing, no infections anywhere. How can I help her?