Considering the amount of testing that you have done...I think that it is safe to say that you are alright physically...and that this is causing you more of an anxiety issue than anything.
Can I recommend these books on health anxiety? You could give them a chance to help, and if are then still at a point with these symptoms that won't let up......you could then pursue more intensive medical investigation.
http://www.amazon.com/Overcoming-Health-Anxiety-David-Veale/dp/1845298241
http://www.amazon.com/Treating-Health-Anxiety-Cognitive-Behavioral-Approach/dp/1572309989
S.C.