What Causes Residual Dizziness After Fever And Headaches?

Hi I became unwell on Tues pm with a fever. I have spent the last 4 days in bed with temp ranging from 100 - 104. Severe headaches, and sickness. I am pleased to say the worst is over, but am concerned that I am still very dizzy when sitting/standing up and feel v weak. My temp is resting around the 99 Mark now. I am worried that there is something else the matter?