I feel really sick when seated and lightheaded. i generally feel better when walking but once seated it comes back. any idea what it is?

Sick and better: I am not sure why this is happening but I strongly recommend you set up an appointment with a Psychologist. She will carefully take your history and make some important suggestions to reduce your concerns. I would appreciate getting some info after you have seen the Psychologist.

Light headed: Some process that would pinch your inferior vena cava when you sit would be an idea.