It's very unlikely that you have colon cancer, given your age...and everybody, IBS or not, gets bouts of diarrhea occasionally. But if you are worried about it, the only way to ease your fears would be to get a colonoscopy. IBS can cause pain in varying regions as well as malformed stools, so it could be as simple as that.
After my appendix ruptured when I was 7, I had bouts of what I like to call the "phantom appendix," where I get sharp pains in my LRQ region...never could figure out what it was, but I figure an ache and pain here or there isn't worrisome. If the pain is consistent and always in the same spot and occurs frequently, you should get it checked out.