should i worry about colon cancer?

i’m a 15 year old male, turning 16 this month & lately i’ve just been worrying about my health, i don’t know why, i’m guessing i’m paranoid, or maybe not, i hope i am though. anyway i’ve lost 38 pounds in one year and whenever people see me they wonder how come i lost all that weight, i was involved in swimming for most the time but stopped around april and i still feel like i’ve gotten thinner after that, i have a family history of colon cancer & i smoke marijuana, sometimes cigarettes but that’s only when i roll the weed onto it i no longer smoke that poison called tobacco though, my finger tips feel extremely cold at night and today i looked at my stool and it was two toned but first time i saw it like that cuz i usually check i’m guessing it’s because i have the flu right now, should i worry?