Thinking more about the on/off med thing... I think it has to do with the fact that when he's ON the meds, he's more likely to follow through with what he has agreed to do. When he's off them, he says he's going to do something (take out the trash, for example), then the next morning after the garbage guys have come and gone, I see the trash still sitting next to the garage door. I would have rather done it myself than have to wait another week with a full trash can in the middle of summer. I've not attributed it so much to ADD as I have to the apathy that takes over with his chronic depression when he's off his meds. But now that I'm learning more about ADD, I wonder if that plays a part - I was slow in accepting his ADD d(x).
I'd rather have him tell me that he's just not going to do something than to let me rely upon him, only to not have whatever it is get done. When he's on his meds, he is good about saying 'no' when he doesn't want to do something, which I appreciate, so when he says 'yes', I believe that he is truly agreeing to do (whatever it is).
It's gotten to the point where I don't feel that I can rely upon him to follow through, so I end up doing more of the shared responsibilities myself. Which, in turn, results in a degree of resentment, which probably DOES come across as nagging.
Sorry - didn't mean to hijack. Just thinking aloud...