It could be lots of things -Crohn's, colitis, a polyp, a fissure, diverticulitis, hemorrhoids. At your age, cancer is probably one of the least likely options and "suspected cancer" doesn't mean they think it's cancer; it just means it's one of the possible options and therefore they have to rule it out. It's medical phrasing and isn't an indication they think it likely. I think they put that any time there's a raised FIT result, although only 10% are cancer and probably less at your age 

the NHS moves pretty quick if it was to be cancer , but like you have put it could be many other things the colonoscopy should tell you more