Welcome and hi! I have a few pesty questions that may help us.
Who diagnosed your son? What kind of professional? Has he seen a Child Psychiatrist (with the MD) or a neuropsychologist?
ODD rarely stands alone. Are there any psychiatric issues or substance abuse on the family tree? Neurological disorders?
How are his social skills, eye contact, any speech or motor delays?
Can you please do a signature, like I did below?
Don't waste time feeling bad. YOU didn't cause this and YOU can't cure him. He needs help beyond you, and he can get it. First off, I'd start with a fresh evaluation to give you a bigger picture of his problem. ODD co-exists with many things.