I'm right there with you...though I realize that's small comfort, if any. I've had to relocate in order to assist my mother, whose memory issues have begun to become more pronounced....and to a part of the country I literally couldnt get out of fast enough, when I left at 17. I feel as though I'm being hunted, behind enemy lines, every time I go to the store, even.
My own mother is in the dreaded "in-between" zone...neither here nor there...not suffering from symptoms pronounced enough for most physicians to be willing to declare her incompetent, and so make possible arranging for a power of attorney to be issued over her affairs...yet suffering enough from symptoms associated with senile dementia to be a danger to herself, however slight.
But as paranoia is often the first symptoms to display in those suffering from senile dementia...attempting to "be there for her enough" to ensure her safety...while at the same time, having no real power over her, to speak of...is maddening, to say the least. Her finances are in disarray, by this point, of course...yet she's too paranoid to allow me, or anyone else, to provide the help she's in dire need of., and without which, she may lose enough to compromise her ability to live comfortably in a secure, managed-care facility of any quality. So I'm right there with you.
I've found I've needed to regiment my life as much as possible...and that this has reduced my stress levels a great deal. But not only "regimentation"...the addition to my schedule of daily activities intended to improve overall outlook and bring a positivity-by-design to my day to day existence--for example....I set aside a period of an hour each morning for reading inspirational literature, ie a "daily reader" of uplifting messages....and included in that hour period, a 30 minute period devoted exclusively to prayer/meditation. I do the same at night...rather, without the reading..and only for around 15-20 minutes, before bedtime. I've begun to include a daily exercise period as well. This is all a "rain or shine commitment", so to speak. Because, believe me...I've never been the sort to do any of the above previously.
But I've realized that dealing with stress is like anything else...more a matter of preparation, than anything. If I wait till it's raining to think about building a house...it's going to be too late, when I'm wet. It took me a long time to make that connection. But I've found it to be very true. It's all the small things I do in between, that act as "deposits in my bank account of stability"...for that rainy day. If I were to just try to wing it, so to speak...I'd have been down and out a long time ago, I feel sure.
Best of luck. feel free to PM me any time.