Homework Blues

How does one motivate a child that has ADD/ADHD to do their homework? I have tried everything from pleading, bribery, crying, and screaming.
I'm beyond frustrated. I just don't know what to do to get him to sit down and do his homework.
Every time I turn around the school is calling me to either complain about him or to inform me that he has detention. When the phone rings, and I see on the caller ID that it's the school, I cringe.
He says he hates school, and he hates his teachers. I've tried telling him that if he will just do his homework, then he can pass the 4th grade. And then he won't have to deal with them anymore.
I just know that I am at my breaking point with all of this. Trying to deal with all of this as well as my bipolar and depression without the aid of medication is difficult to say the least.
I try so hard every day to keep it together. Most days I feel like I'm merely holding on by a thread. And most days I feel like a failure as a mom because I can't get my son to do his homework. And I can almost feel his teachers judging me, and thinking what a horrible mom I am because I can't get my kid to do his homework.