I understand you entirely, OP.
I am someone who needs structure, and expanded structureless time is hard. And it's even harder when you don't have regular human interaction.
There have been times when I've had work trips with breaks set in the middle of them, and I'm in a place all by myself with nothing but free time for a couple weeks. At first it's great, but then you realize you're spending a lot of time chatting to supermarket check-out staff because it's the first person you've spoken to all day. That's tough, and it's very lonely.
My advice, like so many others, is to see whether there's some sort of regular volunteer organization near you. You needn't go every day--even a couple times a week gives your brain something to focus on and look forward to. Personally, I'd do something that has human interaction built in to it, rather than something that might leave you alone and independent. Whether it's volunteering in a room at the National Trust or serving food at a shelter or tutoring kids in the library (I know, coals to Newcastle, but you know you're good at it), something that gives you human interaction for a few hours a day, a couple days a week, will be a godsend.
People underestimate loneliness. And it's compounded enormously by having unstructured time on your hands. I wish you the best.