I had bloody mucus in my stool , irregilar bowel movements, constipation, pain in abdominal area and cramps.

Doctor can examine: Blood in the stool, trouble pooping, abdominal pain, and constipation are symptoms that need to be evaluated by one's primary care doctor or a gastrointestinal doctor. The cause can be a hemorrhoid, an anal fissure, an infection, etc... Tumors or cancers would be very rare in a teen. If the cause is already known by his doctor, a teen can just follow his doctor's care instructions.