what do you do when your spouse is resistant

Short on time trying to squeeze this in whats left of my lunch, but I have a 7 1/2 year old son who has always been on the go. Through the years been told its normal boy behavoir he will outgrow it and so on. Now my DH has never been a believer in ADHD, thinks its an excuse parents and or teachers make. His preschool never had a big enough issue with his activeness but come kindergarten it was more then just that that raised some concerns. He did have a speech issue related to a birth defect that first got him some ed services and long story short we also now get OT and PT all sort of related. A common thread that has varied has been his hyperactivity but each teacher view it a bit different and its peaked and leveled but because of his other issues they did place accomidations in class but they have done all they can do and while yes in kindy and early in first grade while it was more boys being boys as other boys are maturing and calming down so to speak not really DS. They did the final round of educational testing and he passed so now the recomendation is talk to our pedi and look into an ADHD diagnosis and of course DH shuts it down.

So I am at a wall, its not going to stop me, I can't let it my mom did and she regrets it with my sister (she has many issues and as an adult her Dr really feels she was undiagnosed ADHD but my dad never wanted HIS kids in special services) and I've seen where it lead my sister and I don't want that for him. He has so much potention.

Now the irony is last night while I am preparing dinner DH yells at him at least 6 times to sit still and right away when he shoots me down I bring that up and how how do you think he feels and if there is legitametly something wrong and he can't and how do you think that makes him feel about himself and so on. DH immediatly goes on defense on his diet and so ona nd I went off on him. I get not wanting a zombie for a son but been trying to explain thats not the goal and I don't want to go in on all this alone I want him on board but its like getting a mule to move and I am just at a lost. I have made him come to school meetings so he can see what they have already done and that its not them wanting it for them but for him. He has a GREAT OT who is also his coordinator and she fights so hard for him and truly cares but he puts on show for them bits his tongue and then I hear and I just looking for ways to get him to see where we are