Please Offer Thoughts On Strange Symptoms?

I am hoping that people are able to offer suggestions on my condition and possibly share their experiences or offer advice.

I am a 36 year old male in what I think is good physical condition. I am a runner and run 5-8 miles each day except on the weekend when that increases to 10-20 miles.

My problem.

In early february I experienced a terrible bout of diarrhea for about three days. I went to see the doctor and he thought it was a gastrointestinal infection or food poisoning. After about a week the stools became slightly more solid. However, the movements still haven't been normal over three months later.

Please accept my apologies for the graphic description that follows.

I've noticed that my stools are very small in diameter, approximately 1/2" to 3/4" in diameter. The stools do not seem watery but are only just firm enough to retain shape in the bowl. The stools often float and are not well formed but break into millions of pieces when flushed. There is no blood or mucous in the stool that I can see. I do not have any cramps or constant pain. I have slightly changed my diet to include mostly grains, fruits, and vegetables with almost no meat but still eat voraciously.

I saw the doctor many times and each time he said not to worry. I've taken so many blood tests and stool samples that have all come back negative. The only problem was a test called cea that was slightly high at "4.9". The doctor said this test is not usually used for screening and would be higher if something was wrong. He attributed the slightly high level to the gastro infection I had, as the test was completed during the time I had the bout with the infection/food poisoning. I am still very concerned over this result.

I've noticed that over the last five days during a bowel movement the stool will shoot out very narrow and long like toothpaste out of the tube. The diameter is very very narrow, less than 1/2" in diameter. The consistency is very soft (barely holds together) but the color seems normal (light brown or medium brown). There is no mucous or blood that I can see. My energy level is great. I just ran a marathon last weekend with absolutely no problems (under 4 hours).

Are my symptoms consistent with colorectal cancer? Should I be worried and insist on further screening via barium enema or colonoscopy?

Many thanks in advance to those that provide with thoughts or advice!

God bless