Two weeks ago i was feeling dizzy and with a temp.tofixidrank water 3 litres/hour for6 hours for 2 nights straight -i'm 95kg no prv health issues.the tmp got worse, then left, but still light headed and nowbackhead pressure,brainfog - cerebral edema?

You are suffering: from water intoxication. 18 liters of fluid for 2 straight days is way too much. You need to see a dr right away to get this problem resolved. And don't drink anymore like this. It could kill you.

Very unlikely: By far the most likely cause of your symptoms is a viral syndrome, and the headache has to do with tightening of the muscles of your scalp from this infection. If you were developing cerebral edema from any cause, I would look for neurological changes such as nausea/vomiting, blurry/double vision, generalized dizziness. The headache from this cause would increase the longer you lie down as well.