Why do I feel like this all the time

Every time I lay down I get incredibly sick feeling my head gets super hot I feel groggy and just so sick feeling it’s a awful feeling and I feel exhausted like even at physical therapy I’m doing for a car wreck (has been going on for years) and I lay on the table my head gets so heavy and hot and when I sit up it’s like a lot of pressure in my head and it’s absolutely aweful it makes me feel bad for the entire day and I just have to lay in bed which ofcorse makes it worse but I can’t do anything because of how I feel what could this be?