What Causes Sweating, Weakness, Headache And Dizziness?

i have a non-stop headache. my body has no energy, i cant keep much food down, my heart speeds up and then goes back to normal. I have pain that shoots down both arms and legs and i get dizzy when I stand up and try to walk anywhere. My doctor has me on a water pill and a potassium pill. I have been to the ER several times all they do is give me a pain shot and some benadryl and send me home. I keep telling them that something is very wrong. NO one will listen. I feel like at anytime I m going to have a heart attack. I sweat for no reason.