R.C.
I encourage you to examine your diet. A diet high in processed foods (think anything that comes out of a wrapper, box or bag) is really low in nutrients. Consider stopping by your health food store for a good quality vitamin and perhaps some probiotics. About 6 months I felt a lot like you describe, and after going on a strict diet that eliminated processed foods for the most parts in favor of fresh or frozen vegies and meat/fish. I followed it closely for a month and then a relaxed version since. I feel so much more mentally sharp. It's true, to an extent, we are what we eat. I also am up repeatedly at night with a 3 and 2 yr old and I do think that has a lot to do with this "fog" sensation that you describe.