Red in stool with mild located pain near upper left side hip. i've been getting some diarrhea lately & i think my stool is getting thinner. cancer?!

No: Almost with dertainty, no, this is not cancer. At your age, the symptoms you're describing are much more likely to be inflammatory bowel disease symptoms or symptoms of an infection of some sort, than colon/intestinal cancer. See your primary care doctor initially for some basic tests - like is there really blood in your poop- and then they can make appropriate referrals to a GI doctor if needed.