My husband thinks I have dementia. I just have fibro fog. Seems like it is worse when I’m tired.

Your brain fog will come and go in cycles of severity.
I know what you're saying about how worried and upset it can make you.
The way i deal with it now is to openely tell my family that im struggling with brain fog at the moment. That theyre to be patient with me.
Sometimes when its really bad i will just walk away from conversations and seek a quiet activity. Sommething that requires my hands to be busy with no thinking, like the dishes. I use it as a distraction so that it instantly breaks the intense feeling of stress when my brain shuts down.
It took a while for the people around me to understand but its easier now.
If i am out and forget where i am walking or what i am doing, i just stop. If i can sit i will do that. I take some deep breaths and centre myself by doing a technique the psych taught me. I have to use my 5 senses, starting with sight. I look around and rattle off, outloud, 5 things i can see. If ive not remembered what im doing, i take 3 more deap breaths and rattle off 5 things i can feel, touching surfaces as i go.
Usually this helps ground me. If i am calmer by then im able to re trace my thoughts and then i will remember.
I use to worry that i looked like a dick standing in the middle of a busy shopping centre. But now i just make it look like an intentional act and do what i need to to get my brain back.
I hope these tips help you out.
Try to remind yourself that you're just in a cycle right now and it will pass.
Take care, thinking of you.

Yes. the brain fog is so real and so upsetting to me too. Hard to say exactly what triggers it, but I do know that when I get upset about the brain fog...it does get worse. I just have to remind myself that anything, including emotional upset of any kind, causes bad chemicals in the body...inflammation...and makes brain fog, fatigue, soreness, rashes worse. I try then not to lay more work on myself..."If I do x then z won't happen" because that is not true either. Regularly the flares "flare" for no reason whatsoever. But please try to remember to be kind and patient with your self...with your body. You are not alone in this struggle!!!

I can go long periods of time without the fibro fog hitting too bad. But just like the pain, it can be very unpredictable. If you have someone close to you maybe they can help to monitor any changes and you can report to your doc for help.

I have times where the right words are not there. I get embarrassed because names will not click. Even for people I have known forever. Those that know me well help me out with this and laugh with me. It is very frustrating!