Stomach cramps, bloating, abdominal pain, and digestive upset can be early signs of colorectal cancers.LaylaBird/Getty ImagesA doctor said he's seeing a growing number of patients under age 45 with colorectal cancers.He recently treated a 22-year-old with stomach pain. She had a tumor so big it nearly blocked her colon.Symptoms of colon cancer can be subtle, so it's crucial to know the right screening options.The patient was 22 years old and a r…