There are several different things which could cause this kind of symptoms. I would suggest talking to a doctor.

If you are taking medications, talk to the prescribing doctor to see if this type of "brain fog" could be side effects.

If you rule out the meds, you could see a neurologist and see if it's something like dementia (although I am not sure of your age).

I imagine this is really scary for you, but I would encourage you to consult a real doctor and not "Dr. Google." I have spent some time googling symptoms and side effects, and I only end up with increased anxiety and no real answers.