Abdominal discomfort. Old what to do.

I have a very sensitive bowel i suffer diarrhea and constipation since childhood so i have been searching everything on Google though i went to a doctor and did all my tests came back normal one day ate tomatos in dinner in the morning i saw something reddish in the middle of the stool i got worried soo the next i again when to the washroom i wasn't having a bowel movement but still i strained to see weather it was blood or normal stool i strained 5 6 times a day i didn't got anything then got a bowel movement it was normal then again got a bowel movement next day was normal but i feel like not pain but discomfort in my abdomen i am worried everything leads to colorectal cancer i am just 24 years old what to do.