I am new to this website and in search for answers similar to yours. We knew that my son who is almost 10 now had the telltale signs of ODD. He too was diagnosed but ASD was ruled out but not categorically. His behavior worsened with each year but it was never bad enough that it spilled outside of our home. He was always social and behaved when outside barring a few instances.
Fast forward to his ADHD diagnoses and falling behind on his educational milestones, we started him on stimulants. We tried a couple of different medications and dosages but the fall from when the dosage wears off was HORRIBLE. His behavior got noticeably worse and it was obvious that the stimulants were the cause. We stopped the medication to first get his behavior slightly in control. The first couple of weeks were better but then it took a turn for the worse. Every evening was a nightmare with him breaking down. We followed the rule book of not breaking down ourselves and not get upset at all – instead comfort him and show that we love him. It did not help.
After visiting the psychiatrist, we started him on Intuniv. It has definitely helped some but he needs therapy to go along with it. He starts CBT this weekend so we are hoping it helps more. I would like for him to start stimulants at one point because Intuniv does not help much with his attention disorder.
I wrote all of this to say that you are not alone and also to see if you have ever tried taking him off of stimulants to see if his behavior improved? Please do talk to the doctor about it before you take any action. Alternately have you looked into drugs such as Abilify?