a 26 yrs old female comes and complains of having sudden gut pain and feeling the need to stool but she also says that she don't have constipation or diarrhea. She explains that eating fibers or drinking less water causes her constipation easily and if she eats gluten or lentils then she gets diarrhea. what does she have? how to screen out diseases and confirm hercondition? and what tests are required?