My great uncle was an MD and 50 years ago, when the fad of "cholesterol is bad!" started, his take on it was that the brain is made primarily fats and cholesterol. Cholesterol circulating in your bloodstream is a sign that you have plenty where it's needed....so reducing that is stupid since it will alter the makeup of the brain. He was ahead of things, as now there are studies that show that blood cholesterol numbers are meaningless as far as overall health, and he refused to treat his 'high cholesterol'. He lived to his late 80's, sharp as a tack and mostly physically able as well.
If you're taking meds to reduce your blood cholesterol, do some research into whether you should be doing so.
Another sneaky culprit that can cause memory issues is antihistamines. My mom would drink Benadryl for her allergies, and it caused plenty of brain fog. Sis and I call it Roomba medicine, because she'd get to the point of aimlessly wandering. So we picked up a generic diphenhydramine, poured it out and replaced it with Big Red. Within a month she was back to normal and never went after an antihistamine again.
Just a couple of suggestions, I don't know if either would apply to your situation or not, but I'd rather toss 'em out there than wish I had!
Best to you, and prayers sent up!