It's extraordinarily unlikely to be bowel cancer at your age. It is far, far, far more likely to be IBD, which typically strikes teenagers and young adults. Blood markers can be normal in IBD, while faecal calprotectin is usually raised, at least during a flare-up.
Dx Crohn's in summer of 2000. (Yay )
Tried and failed: 5-ASAs, Azathioprine, 6MP, Remicade, Methotrexate, Humira.
Diet didn't make any difference either.
Had surgery 2/13 - subtotal colectomy with end ileostomy. Currently on no meds and in remission. Also prone to depression and anxiety. Ask me anything >_>