Such behavior, called palilalia, is often seen in children who display OCD. You may be involved in a futile attempt when you expect him to tell you about something that is bothering him - that is not likely to occur. Regard it as simply another aspect of his OCD. Has he been evaluated by a child psychiatrist, and is he taking any medication for his condition? The standard of care for OCD is a combination of pharmacological treatment and cognitive behavioral therapy. Some bibliotherapy might also be useful - take a look at Touch and Go Joe, Mr. Worry: A Story about OCD, Talking Back to OCD and also the workbook What To Do When Your Brain Gets Stuck.