A few pieces of info for you.
First, as somebody who gets diarrhea a lot, cramps have little relation. I've never had cramps associated with diarrhea. Is it possible that some people get cramps every time they have diarrhea? Sure. Everybody's body is different. But don't think diarrhea without cramps means anything ominous. It doesn't. Stool consistency is what it is.
Second, the idea that stool shape (narrow, flat) has anything to do with colon cancer is outdated and probably incorrect, working off an unsubstantiated theory from the 1800s with no viable evidence to back it up. Constant diarrhea or constipation, especially with constant blood (usually black and tarry, but can be bright red), on the other hand can sometimes be a symptom of colon cancer, though not always. Colon cancer is often a silent killer with no noticeable symptoms.
At your age (33), colon cancer is extremely unlikely. Impossible? No. But extremely unlikely. Like winning the lottery unlikely. For your age bracket (29-35), less than 1,000 cases will be diagnosed each year in the U.S. (don't know the statistics abroad, but would imagine they are a similarly low percentage). And many of those 1,000 cases will be predisposed to colon cancer by having a genetic anomaly that causes an abnormal amount of polyps. This genetic condition runs in families, so you'd know if you had it. So very, very rare to have colon cancer at your age.
Here's what your doctor is going to look for before sending you in for a costly colonoscopy that you *more than likely* don't need. He/She is going to ask you about your bowel movements, take a look down there, maybe do a flex sig (an instrument that inspects the rectum), investigate your diet, probably do a CBC (complete blood count) test to test your white blood cells and for anemia, and ask about weight loss.
If these tests are normal, you will probably be diagnosed with IBS and told to take it easy. If they are abnormal, they will investigate further. It is not very likely they will order a colonoscopy without constant blood in the stools and presence of anemia.
At your age, if you haven't lost a lot of weight quickly (10+ pounds), don't have blood in your stools, aren't anemic, don't feel severely fatigued, and don't present with serious chronic pain, the chances you have colon cancer are next to none. Diarrhea is often just diarrhea. Stress, anxiety, lifestyle, etc. Of course, if it's persistent (all the time), it should get checked out. Which you're doing. And that's the hard part. But please try and relax and realize the odds are astronomically in your favor.
Hope this helps comfort you! Feel free to message me if needed.