What Causes Lightheadedness And Dizziness?

Hi. I m 21 year old male. I always feel lightheaded and dizzy while sitting, lying down, standing and walking. Even I have a good night sleep, I still feel lightheaded when waking up. I jog every other day and feel lightheaded after exercise. I visited a neurologist 2 weeks ago, had CT head scan done without contrast. And it came back normal. I don t know what to do.