Oof! That’s so hard, but I think we all totally get it. Whether for ourselves or for our kids, we’ve all been in that, “but what if it’s dangerous?” spot when it comes to “controlled substances.”
I think the other comments are very thoughtful and thorough. I will only add that you will need to break the problem down into smaller chunks and identify which chunks you have control over and which you don’t. A HARD ask for untreated ADHD!
What is it they are afraid of? What can you offer to ease those fears? Would it be helpful to give them a sense of control? Maybe they can keep the meds in a locked cabinet only they can access to give you your doses?
Or, if they’re really dug in about it, you may have to go this one alone. Seek out forums for self-treating your ADHD with diet and exercise. Getting started is the hardest part (even on stimulant meds, I can’t get motivated to exercise). You can all but “cure” yourself with exercise. (My mom was never diagnosed, but running almost obsessively, you’d never know.)
I hope you are eventually able to access whatever will work for your brain!