My son, 6 yrs old, was diagnosised with OCD and Tourette Syndrome this past summer by a child neurologist. We are learning how to live with his OCD, there are certain things if not done correctly will cause an outburst of yelling, throwing things.. I try to keep a record of what leads upto his outbursts or what may triggered them to try to difuse the problem the next time before it causes an outburst. Believe me, my husband and I have tried everything with him and it is exhausting, it causes much turmoil in our household.
After much research I have learned that ADHD goes along with OCD and Tourette Syndrome. Have you taken your son to see a child neurologist? If not perhaps you should take this into consideration. Our son's psychologist referred us to one. After reading many books, I discovered a book, The Explosive Child by Ross W. Greene, Ph.D., it was if the book was written for us. I am only half way through it, but I strongly suggest this book. It's encouraging to know that my son is not acting badly just because he chooses too, but that he has problems with problem solving, frustration and inflexiblity.
I wish you well. Just remember you are not alone, there are many of us mothers who are experiencing situations similar to you.