As far as the pain on the left side of the body is concerned, if the whole left side was involved, without localization to joints, sudden in onset with persistence of symptoms
, it seems very much like a stroke
. One possibility for negative reports that I can think of is that you had a spasm of blood vessels or your investigations were done before the stroke progressed to a level where changes are visible on the scans. This ties in with the fact that you also have memory problems.