20 yeаr оld Jаke whо is а Hispanic cоllege student, comes to the office today for his yearly exam. Jake reports that he has had several episodes of diarrhea at school over the last two years. He gets a lot of cramping, but improves a great deal after he expels the diarrhea. Sometimes his stools do change in consistency and he will also pass mucous but no blood. Per the Rome or diagnostic criteria, his most likely diagnosis is?