I completely agree with your doctor who booked you for colonoscopy
as vague symptoms like you are describing, better to rule out any cancerous growth inside. Overall I understand you have IBS/ diverticular disease
and your concern is that whether cancer can exaggerate the symptoms if it occurs at the same place. This I don't think anyone has concrete evidence about and one can't reply with any certainty. I would not worry too much if colonoscopy comes as normal.
Take care, Regards