Hi My Faith,
Everything you said sounds familiar to me! How old are you? I am 54 and this is the first year I've missed a few periods...although the last 2 have come right on time

But oh yeah..the brain fog thing! Its VERY weird! I forget what I was going to a certain room for. I'm getting horribly forgetful as to whether I took my prescription pill in the morning..thank goodness I put it in one of those "days of the week" containers you get at the drug store! I can literally take a pill in the morning, and 30 minutes later, don't remember if I took the pill or not (unless its in the special container). Its definitely brain fog. I have felt lightheaded and off balanced slightly, from time to time. I get very pms-y, and yet sometimes I don't, and lately I've been very calm about most things. I'm not experiencing hot flashes right now, after I did for a few months..probably because my periods are coming regularly again.
When I went to my gynecologist in June..the VERY FIRST THING he asked me when he came in the room was "Do you have The Brain Fog thing?" !! I was so surprised about that! I thought he'd ask more about the physical symptoms first..like hot flashes, bleeding problems, etc. He KNEW about the brain fog!!!! I thought "Here is a male doctor who KNOWS, and understands, and GETS IT"! Its all normal...although taking hormones might help. I'm not on anything, and don't feel the need, would rather go thru this naturally. But it might help?
Good luck to you!!!