Welcome! I'm glad you found us.
Sorry for all the questions, but your answers will help us point you in the right direction for help.
What kind of doctor is evaluating and diagnosing your son?
What symtpoms are you seeing that concern you?
How does he do in school, both academically and with peers?
Any mental health issues or substance abuse in the family tree?
Any sensory issues (sensitivity to clothing, loud noises, food textures, for example)?
Any speech or developmental delays?
Generally, ODD is not a stand-alone diagnosis, but a symptom of an underlying disorder. Once the underlying disorder is identified and treated, the oppositional behaviors typically subside.
A book that is highly recommended around here is The Explosive Child by Ross Greene. It has helped many of us parent our extra-challenging children.
Again, welcome.