I am sooo glad you found us. I, too, have found wonderful advice and great strength here. There isn't a situation that has ever come up that others here have not been through. Good luck with the evaluation. Signs of Obsessive Compulsive Disorder (OCD) are also some of the symptoms of Autism Spectrum Disorders (ASD) and ODD so don't be surprised. My difficult child has been diagnosed with ADHD, ODD, and Anxiety. The more I read here and research Autism Spectrum Disorders (ASD), it makes total sense to me that his ODD and Anxiety are actually his reactions to situations that are because of Autism Spectrum Disorders (ASD). We are working on LEARNING the skills he is lacking.
The only advice I have is to be patient and keep notes on behaviors, precursors, reactions, etc so you have more information for the professionals to get a true picture of your son. I would also highly recommend Ross Greene's book "The Explosive Child". Everyone here recommended it and it's one of the most helpful resource and "bible" I have read.
Again, welcome to the family.