What Causes Fatigue And Dizziness After The Treatment Of Upper Respiratory Infection?

I can t seem to get a doctor to diagnose what I have. I started with upper respiratory Dec. 2. A steroid treatment made me feel better over holidays. Since then I have been exhausted, dizzy, off balance, nausea at times. I was put on amoxillan a few weeks ago which gave me diarrhea and then vertigo. Then they thought I might have C-diff so now I m on another antibiotic which has caused a yeast infection. Overall, my entire body aches, I can hardly move, I feel weak, I don t want to hold my eyes open and this is after a sound 9 1/2 hours of sleep. I can t get anything done as I can t stay focused and I m so off balance it s hard to move around. I was in the hospital where they did a chest x-ray and hords of blood work which was all fine except my magnesium which has been low for years even though I take 800 mg supplement a day.