hi,
these symptoms sound to me like a mild panic disorder...i've had full blown panic attacks and they start out like your symptoms do....feeling unreality,
trouble catching my breath, dizzy like i could fall or like the floor is moving, cold and hot sweats, shaking ect..ect..
do you feel nervous at all? are you under alot of stress? my panic attacks started when i was about 25 or so...had no idea what was wrong with me.....thought it was my heart .....was scared spitless. see your doctor again if you think this might be the problem.....he can help you calm down with meds..........hope this helps a little peace