Sharon, first of all, "A mother is a mother, is a mother, is a mother." In other words, you don't stop being a mother just because your "child" is a "grown up!" You are showing your love and concern for your son, and I think there isn't anything to feel guilty or self-conscious about. (As an adult, he certainly has the right and the ability to tell you to "back off" if he wishes. So, you should be free to tell him how you feel, and he should be free to do likewise. The dynamic between you two is a private matter to be worked out within the family.)
OK, his symptoms.... Could just be that he's straining with that early morning stool; if he's very constipated AND he has disc problems in his spine, that could result in quite a bit of discomfort for him, even lasting throughout the day. I don't have enough information from what you wrote to really comment on much more, other than to agree that, with your family's strong history of colon cancer, and your son's complaints, a proactive investigational appraoch, as is being conducted, is a very good idea.
I wish him well.
Hope