Frequent Diarrhea and stomach aches?

Okay embarrasing but i've got to get an answer. For the past year or so i've been getting terrible stomach aches. Im very healthy hardly ever eat fast food and I drink plenty of water. Lately ive been getting diahhrea atleast once a day i never told the docter that but he did diagnose me with ibs, i personaly think its got to be more with the stomach pains i get and the frequent diahrreah and sometimes upper abdomane. What should i do? get a colonoscapy? what could it be? Colon cancer?