ADHD or Shitty parent...which one is it?

We've had the flu this weekend. I think we're finally at the tail end of it - but it's been a tough one. I was the second man down...not fair for a mom. We're supposed to be last man standing. We almost have to be, but anyway...I wasn't. But, this weekend really impressed on me that there I have a legitimate reason to be concerned with my son.

An 8 year old child should be able to process a request and the reason for the request and comply with said request. Shouldn't he?? Now a 4 year old...meh. 5 year old - depending on maturity... 6 year old - we're starting to get into no brainer territory here. You should be able to say to an 8 year old "Please keep your voice down, Sarah, mom and Meghan are all sick and need to rest." But, you can't.
This morning alone, Michael told him to quiet down at least 10 times. At 7 in the morning. It usually goes a little something like this. "Josh, hush." "Josh, quiet please." "Josh, come on man, your mom and the babies are still sleeping." "Josh, knock it off, what did I just tell you?" "Josh, you need to stop talking." "Josh, quit making that noise." "Josh, SHUT UP!!!!!" and even then...nothing. I know he hears, cause we've done those tests too.

So, I came downstairs this morning with an epiphany. All these wasted years of me thinking that Josh's issues stem from my shitty parenting are just clouding the subject. The subject being that maybe there is something wrong with Josh. Maybe there is a neurological reason he is unable to process basic requests. Maybe it's not all about me. Maybe the people who think that I'm the reason for his behaviour can go sit and spin, since I am able to raise 3 other children rather calmly. Particularly the people who don't have children but think they have all the answers on how to raise them. So wise.
I have been ground down to the fracking bone with this child. All of my parenting resources are exhausted. No one comes with a manual, but honestly, I'm a pretty good, consistant, fair but firm mom with my other children. I've been told that I treat Josh differently. Josh is different. Not sure what I'm supposed to do with that? I'm tired of being judged. I don't have to raise my voice to Sarah. She complies. She asks a question, gets an answer, positive or negative and carries on with her day. Life does not revolve around Sarah. I don't know about the babies yet, because they're just that, babies, but neither one of them is showing the will that Josh demonstrated at 2.
So, I guess it's time to dig a little deeper. The pediatrician says he has it. I don't believe she looked deep enough. If he has it, he has it and I'm fine with that, but I'm not taking a diagnosis because a show of hands indicated that he drives them crazy too. I guess it's time to see a psychologist/psychiatrist. Things need to change. I'm going to explode if they don't. I can't bare the brunt of this responsibility any longer. I makes me so sad that when he leaves the house for school, the whole place changes. I can let my guard down. He thinks I hate him. Which is very basic, 8 year old thinking. He's wrong. I love him so much, but I can't afford to let him rule the world any longer. I love him enough to know that he doesn't have the fortitude it takes to be the commanding presence in our home. It's time for the table to turn back to their rightful places. Maybe he can find some rest in being the child? I don't know where to start, but I have a doctors appointment in mid March, so that might be the place to get some info.
This weekend away is sooooooooooooo needed.