A simple X-ray image (native image) of the abdomen can’t detect colon cancer, but it can tell us if there is some intestinal obstruction present, or not. If there is an obstruction present, you can then research the possible cause of the obstruction, including colon cancer.
More information about colon cancer can be gathered via an irigography. Irigography is a contrast X-ray method where the X-ray image is taken after filling the colon with contrast (barium) through the anus.
The best method for detecting colon cancer is via a colonoscopy. A colonoscopy is an endoscopic procedure wherein the colon is seen from a camera placed on the top of a fiber-optic, flexible tube that is inserted in the anus. During a colonoscopy, the doctor performing the procedure is able to take some tissue samples (biopsy) for hysto-pathologic analyses if and when s/he notices any suspicious tissue in the colon.
An abdominal ultrasound and CT-scan are done to detect regional spread of colon cancer.
Further, a very useful laboratory method for assuming colon cancer is to use an occult blood test of the stool. This test detects very small amounts of blood in the stool (visually unnoticeable) that might originate from colon cancer. The occult blood stool test should be performed first, and then the other imaging methods follow.
Symptoms of colon cancer depend upon its location. Cancers of the left colon (colon descendent) manifest earlier in the disease, with symptoms of bowel obstruction (constipation, vomiting, abdominal pain). Cancers of the right colon (ascendent colon) may show no symptoms until the disease had spread. That is because right colon is thicker than the left one. Losing weight could be the first symptom of right-sided colon cancer. Blood in the stool can be present in both types of cancer, but it is often invisible. Occult blood test can detect such small amounts of blood in the stool.
According to your symptoms (“pain and slight swelling in the front of my lower left rib cage area which radiates to middle back”, “lower back muscular pain”, “gases and narrow stool”), it doesn’t seems likely that you have colon cancer but you may do some of the diagnostic procedures mentioned above. You can consult an internist if you like.