First, please address the chronic distress ASAP by drawing healthy boundaries for yourself. Let other people at work and/or home share some of the health risks you are bearing by yourself here, if possible.
Chronic stress, to say nothing of distress, is associated with cognitive decline, so please at least consider that.
Second, I hope you'll consider planning as a set of specific, defined activities that can be done in a known time period. It may take some practice, but typically the most effective planner's mindset is something like "this usually takes N minutes and will result in a new or adjusted schedule."
The "enticing idea" of global planning-need can really, really be a mental drag at first because it feels like a great way to move on (it is) but it's also really vague, so I think it's important to define and know exactly what activities planning will involve for you (not even so much what you need from it) and how long that will take.
This should get you to the point where you can do big-picture planning every day if needed, and therefore feel like you have serious traction.
When I make plans, I start by writing my status. Because stress may be involved, and lower-brain emotive components, I _always_ vent a bit to start. In my experience, people who can vent and complain faster will generally have faster access to change. So I start by doing that, and pretty soon the data-flow begins--what needs to change specifically. What needs to be done next.
So I go back and underline those things, then I carry them over into either a list (daily or weekly scope usually) or a concept map / mind map in my own style (weekly through yearly scope for example).
This then needs to be made amenable to calendaring, so each item or topic is given a text file if it doesn't already have one. This text file has a "current position" section with the general position of things and the next step. The step is placed on the calendar. I also use programmatic tools to parse these files for tags so I can get the output in my text editor.
Anyway, that, or the ideas in there, should help you get a good start from where you're at. Again please go to work immediately to reclaim your energy, and focus & positive change will likely follow. GL & hang in there.