I'm having intestinal/ abdominal distress?

For the past 2 years I've been having trouble. It all started in 2016 when I changed my diet. I was eating a pound of chicken breast every lunchtime. For months, I was always constipated. When I stopped the chicken breast, the constipation lessened but at one point there was a long streak of blood on my stool. I opted to go to the doctor. I did a test for parasites and that came back negative. I don't mean to me raw, but I have alternating bouts of constipation and diarrhea. Some days I don't poop at all then other days I poop up to 4 times. When the stool is large, I can literally feel it pressing against my rectal walls csusing slight pain. I can feel the flatulence travelling too and I often have to force to get the gas out. Mucus is in my stool and the stool tends to be pale/yellow. No blood in the stool nowadays. Stools are sometimes thin and long. Abdominal pain can be slight to the point it's unnoticeable and can be so bad that it's paralyzing. I feel that the issue could be diagnosed with a colonoscopy as it seems to me the issue is a large intestine issue. What am I showing symptoms of? I've been suffering for 2 years now. What should I do?