This may be a dumb idea as it may force a discussion with your sisters, but can you give them the painkillers to keep with them and just give when required.
This way you only give then enough for a week and they can only give when required. I'm not sure if that's an option for you though. Just thought I'd mention it. ((((HUGS))))
It is an option. A great one. I have one sister I could ask to do it. Problem is that if I give anyone the painkillers I have, um, they'll completely freak out, with very good reason. If someone would ask me to hold the amount I have for them and give them only when they need I don't know how I'd react, because it's way too much to be normal/safe in a way.
Also, I can always get more. Even if not what I ideally want I figured how to get the non-ideal in an easier way than what I ideally want. I don't honestly know how I'd react if I use safely. If it'll be triggering or not. It's something I wonder about. It may be okay, it may not. I think I'd have to wait until I'm in a really okay place (and when I don't have anything at all in reach) to try it.
It is something I can apply though. For I want to ask my dr about sleeping. And I don't think it's safe for him to give my anything. But if someone else would have it and give me only one just when I want it, it may be okay.