Why Do I Feel So Fatigued, Headachy And Awful All The Time?

Hi - I am a 55 yo female. A mail in fecal test was positive but I never did a colonoscopy. My stools are narrow and light. I ve been vegan for several years, I do 4 hours of cardio/day, I don t do drugs, don t drink/smoke, don t eat sugar or gluten. I feel like crud all the time. I take iron supplements and whole food vitamins. I eat only vegetables, nuts and some fruit. Why do I feel so fatigued, headachy and awful all the time? Thanks!