I hate office politics. This is really what is keeping you from directly telling them.
I think you eventually should tell them, just wait until a quiet moment arrives between this current mess (which has nothing to do with your ADD, and everything to do with someone else’s bad timing), and the next huge office drama.
As for finding a way to deal with it for now, you can take a small pad or pocket notebook with you and keep it at work. Write instructions down as you receive them. Just explain you want to get things down clearly. If you can’t do that, try the whole active listening thing (I usually hate this, because it’s somewhat corny, but it may work for you, in this case). When you get instructions, find a way to repeat them back to the boss, again, saying something like “Just so I’m clear, what you need from me is…” Active listening is also a great way to force yourself to pay attention.
When this all simmers down, and whatever solution to the last problem is working well, before the next problem arises, you might mention it. You also may be asked why your suddenly writing things down, or repeating questions, and if this last mess is out of the way, you maybe could tell them that you are working on your ADD.
Be careful to explain what it is, though. Twice now, when I’ve told people, they think I have severe depression or autism. I think one thought I was suicidal. People get their acronyms mixed up. LOL!!!
Good luck! Work sucks…ADD or no ADD. I’m so not looking forward to rejoining the workforce 