This may very well be metal toxicity.
However, speaking from actual personal experience of heavy metal intoxication, metasl toxicity's eefects upon cognition are quite interesting.
Metal toxicity can act directly upon neuronal function but metal toxicity can also disable certain enzyme pathways within the liver and this can lead to the liver being unable to detoxify certain compounds within foods, such as Tyramine. Tyramine is in many foods - yeasts, fruits, nuts, seed, cheeses etc. If I consume a food with tyramine in it, I experience headaches and extremely fuzzy/foggy cognition within just a minute or two of consuming it.
So, I would recommend you keep a food diary and that you read up on which foods contain tyramine. Tyramine isn't necessarily an issue for you, but it might be exacerbating some of your symptoms, just as it does mine.
Moreover, I STRONGLY recommend you join the Frequent Dose Chelation Group on Yahoo! Groups. This group is wonderfully helpful and they focus upon SAFE chelation using the Cutler Protocol.
PLEASE don't try using cilantro (coriander) or chlorella, no matter who you see extolling its use for heavy metal detoxification, be they patients or even famous practitioners (eg Dr Klinghardt) - cilantro in particular is an extremely dangerous substance because it moves metals into the CNS in an uncontrolled manner.
Andrew Hall Cutler, on the other hand, is someone whose work you should pay great attention to (www.noamalgam.com).
I'm not saying any of the above because I read it in a book. I'm saying it because I am walking the path of heavy metal intoxication myself.
Good luck.
PM me if you need any further assistance and I'll be more than happy to help you avoid the numerous pitfalls out there for metal-intoxicated folks.